summaryrefslogtreecommitdiffstats
path: root/html/postconf.5.html
diff options
context:
space:
mode:
Diffstat (limited to 'html/postconf.5.html')
-rw-r--r--html/postconf.5.html20844
1 files changed, 20844 insertions, 0 deletions
diff --git a/html/postconf.5.html b/html/postconf.5.html
new file mode 100644
index 0000000..683cdb7
--- /dev/null
+++ b/html/postconf.5.html
@@ -0,0 +1,20844 @@
+<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN"
+ "http://www.w3.org/TR/html4/loose.dtd">
+
+<html>
+
+<head>
+
+<title>Postfix Configuration Parameters </title>
+
+<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
+
+</head>
+
+<body>
+
+<h1><img src="postfix-logo.jpg" width="203" height="98" alt="">Postfix Configuration Parameters </h1>
+
+<hr>
+
+<h2> Postfix main.cf file format </h2>
+
+<p> The Postfix main.cf configuration file specifies a very small
+subset of all the parameters that control the operation of the
+Postfix mail system. Parameters not explicitly specified are left
+at their default values. </p>
+
+<p> The general format of the main.cf file is as follows: </p>
+
+<ul>
+
+<li> <p> Each logical line is in the form "parameter = value".
+Whitespace around the "=" is ignored, as is whitespace at the end
+of a logical line. </p>
+
+<li> <p> Empty lines and whitespace-only lines are ignored, as are
+lines whose first non-whitespace character is a `#'. </p>
+
+<li> <p> A logical line starts with non-whitespace text. A line
+that starts with whitespace continues a logical line. </p>
+
+<li> <p> A parameter value may refer to other parameters. </p>
+
+<ul>
+
+<li> <p> The expressions "$name" and "${name}" are recursively
+replaced with the value of the named parameter. The parameter name
+must contain only characters from the set [a-zA-Z0-9_].
+An undefined parameter value is replaced with the empty value. </p>
+
+<li> <p> The expressions "${name?value}" and "${name?{value}}" are
+replaced with "value" when "$name" is non-empty. The parameter name
+must contain only characters from the set [a-zA-Z0-9_]. These forms are
+supported with Postfix versions &ge; 2.2 and &ge; 3.0, respectively.
+</p>
+
+<li> <p> The expressions "${name:value}" and "${name:{value}}" are
+replaced with "value" when "$name" is empty. The parameter name must
+contain only characters from the set [a-zA-Z0-9_]. These forms are
+supported with Postfix versions &ge; 2.2 and &ge; 3.0, respectively.
+</p>
+
+<li> <p> The expression "${name?{value1}:{value2}}" is replaced
+with "value1" when "$name" is non-empty, and with "value2" when
+"$name" is empty. The "{}" is required for "value1", optional for
+"value2". The parameter name must contain only characters from the
+set [a-zA-Z0-9_]. This form is supported with Postfix versions
+&ge; 3.0. </p>
+
+<li> <p> The first item inside "${...}" may be a relational expression
+of the form: "{value3} == {value4}". Besides the "==" (equality)
+operator Postfix supports "!=" (inequality), "&lt;", "&le;", "&ge;",
+and "&gt;". The comparison is numerical when both operands are all
+digits, otherwise the comparison is lexicographical. These forms
+are supported with Postfix versions &ge; 3.0. </p>
+
+<li> <p> Each "value" is subject to recursive named parameter and
+relational expression evaluation, except where noted. </p>
+
+<li> <p> Whitespace before or after each "{value}" is ignored. </p>
+
+<li> <p> Specify "$$" to produce a single "$" character. </p>
+
+<li> <p> The legacy form "$(...)" is equivalent to the preferred
+form "${...}". </p>
+
+</ul>
+
+<li> <p> When the same parameter is defined multiple times, only
+the last instance is remembered. </p>
+
+<li> <p> Otherwise, the order of main.cf parameter definitions does
+not matter. </p>
+
+</ul>
+
+<p> The remainder of this document is a description of all Postfix
+configuration parameters. Default values are shown after the
+parameter name in parentheses, and can be looked up with the
+"<b>postconf -d</b>" command. </p>
+
+<p> Note: this is not an invitation to make changes to Postfix
+configuration parameters. Unnecessary changes are likely to impair
+the operation of the mail system. </p>
+
+<dl>
+<DT><b><a name="2bounce_notice_recipient">2bounce_notice_recipient</a>
+(default: postmaster)</b></DT><DD>
+
+<p> The recipient of undeliverable mail that cannot be returned to
+the sender. This feature is enabled with the <a href="postconf.5.html#notify_classes">notify_classes</a>
+parameter. </p>
+
+
+</DD>
+
+<DT><b><a name="access_map_defer_code">access_map_defer_code</a>
+(default: 450)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code for
+an <a href="access.5.html">access(5)</a> map "defer" action, including "<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>"
+or "<a href="postconf.5.html#defer_if_reject">defer_if_reject</a>". Prior to Postfix 2.6, the response
+is hard-coded as "450".
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+<p>
+This feature is available in Postfix 2.6 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="access_map_reject_code">access_map_reject_code</a>
+(default: 554)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code for
+an <a href="access.5.html">access(5)</a> map "reject" action.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_cache_cleanup_interval">address_verify_cache_cleanup_interval</a>
+(default: 12h)</b></DT><DD>
+
+<p> The amount of time between <a href="verify.8.html">verify(8)</a> address verification
+database cleanup runs. This feature requires that the database
+supports the "delete" and "sequence" operators. Specify a zero
+interval to disable database cleanup. </p>
+
+<p> After each database cleanup run, the <a href="verify.8.html">verify(8)</a> daemon logs the
+number of entries that were retained and dropped. A cleanup run is
+logged as "partial" when the daemon terminates early after "<b>postfix
+reload</b>", "<b>postfix stop</b>", or no requests for $<a href="postconf.5.html#max_idle">max_idle</a>
+seconds. </p>
+
+<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
+(weeks). </p>
+
+<p> This feature is available in Postfix 2.7. </p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_default_transport">address_verify_default_transport</a>
+(default: $<a href="postconf.5.html#default_transport">default_transport</a>)</b></DT><DD>
+
+<p>
+Overrides the <a href="postconf.5.html#default_transport">default_transport</a> parameter setting for address
+verification probes.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_local_transport">address_verify_local_transport</a>
+(default: $<a href="postconf.5.html#local_transport">local_transport</a>)</b></DT><DD>
+
+<p>
+Overrides the <a href="postconf.5.html#local_transport">local_transport</a> parameter setting for address
+verification probes.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_map">address_verify_map</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+Lookup table for persistent address verification status
+storage. The table is maintained by the <a href="verify.8.html">verify(8)</a> service, and
+is opened before the process releases privileges.
+</p>
+
+<p>
+The lookup table is persistent by default (Postfix 2.7 and later).
+Specify an empty table name to keep the information in volatile
+memory which is lost after "<b>postfix reload</b>" or "<b>postfix
+stop</b>". This is the default with Postfix version 2.6 and earlier.
+</p>
+
+<p>
+Specify a location in a file system that will not fill up. If the
+database becomes corrupted, the world comes to an end. To recover
+delete (NOT: truncate) the file and do "<b>postfix reload</b>".
+</p>
+
+<p> Postfix daemon processes do not use root privileges when opening
+this file (Postfix 2.5 and later). The file must therefore be
+stored under a Postfix-owned directory such as the <a href="postconf.5.html#data_directory">data_directory</a>.
+As a migration aid, an attempt to open the file under a non-Postfix
+directory is redirected to the Postfix-owned <a href="postconf.5.html#data_directory">data_directory</a>, and a
+warning is logged. </p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#address_verify_map">address_verify_map</a> = <a href="DATABASE_README.html#types">hash</a>:/var/lib/postfix/verify
+<a href="postconf.5.html#address_verify_map">address_verify_map</a> = <a href="DATABASE_README.html#types">btree</a>:/var/lib/postfix/verify
+</pre>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_negative_cache">address_verify_negative_cache</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Enable caching of failed address verification probe results. When
+this feature is enabled, the cache may pollute quickly with garbage.
+When this feature is disabled, Postfix will generate an address
+probe for every lookup.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_negative_expire_time">address_verify_negative_expire_time</a>
+(default: 3d)</b></DT><DD>
+
+<p>
+The time after which a failed probe expires from the address
+verification cache.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_negative_refresh_time">address_verify_negative_refresh_time</a>
+(default: 3h)</b></DT><DD>
+
+<p>
+The time after which a failed address verification probe needs to
+be refreshed.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_pending_request_limit">address_verify_pending_request_limit</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> A safety limit that prevents address verification requests from
+overwhelming the Postfix queue. By default, the number of pending
+requests is limited to 1/4 of the <a href="QSHAPE_README.html#active_queue">active queue</a> maximum size
+(<a href="postconf.5.html#qmgr_message_active_limit">qmgr_message_active_limit</a>). The queue manager enforces the limit
+by tempfailing requests that exceed the limit. This affects only
+unknown addresses and inactive addresses that have expired, because
+the <a href="verify.8.html">verify(8)</a> daemon automatically refreshes an active address
+before it expires. </p>
+
+<p> This feature is available in Postfix 3.1 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_poll_count">address_verify_poll_count</a>
+(default: normal: 3, overload: 1)</b></DT><DD>
+
+<p>
+How many times to query the <a href="verify.8.html">verify(8)</a> service for the completion
+of an address verification request in progress.
+</p>
+
+<p> By default, the Postfix SMTP server polls the <a href="verify.8.html">verify(8)</a> service
+up to three times under non-overload conditions, and only once when
+under overload. With Postfix version 2.5 and earlier, the SMTP
+server always polls the <a href="verify.8.html">verify(8)</a> service up to three times by
+default. </p>
+
+<p>
+Specify 1 to implement a crude form of greylisting, that is, always
+defer the first delivery request for a new address.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+# Postfix &le; 2.6 default
+<a href="postconf.5.html#address_verify_poll_count">address_verify_poll_count</a> = 3
+# Poor man's greylisting
+<a href="postconf.5.html#address_verify_poll_count">address_verify_poll_count</a> = 1
+</pre>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_poll_delay">address_verify_poll_delay</a>
+(default: 3s)</b></DT><DD>
+
+<p>
+The delay between queries for the completion of an address
+verification request in progress.
+</p>
+
+<p>
+The default polling delay is 3 seconds.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_positive_expire_time">address_verify_positive_expire_time</a>
+(default: 31d)</b></DT><DD>
+
+<p>
+The time after which a successful probe expires from the address
+verification cache.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_positive_refresh_time">address_verify_positive_refresh_time</a>
+(default: 7d)</b></DT><DD>
+
+<p>
+The time after which a successful address verification probe needs
+to be refreshed. The address verification status is not updated
+when the probe fails (optimistic caching).
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_relay_transport">address_verify_relay_transport</a>
+(default: $<a href="postconf.5.html#relay_transport">relay_transport</a>)</b></DT><DD>
+
+<p>
+Overrides the <a href="postconf.5.html#relay_transport">relay_transport</a> parameter setting for address
+verification probes.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_relayhost">address_verify_relayhost</a>
+(default: $<a href="postconf.5.html#relayhost">relayhost</a>)</b></DT><DD>
+
+<p>
+Overrides the <a href="postconf.5.html#relayhost">relayhost</a> parameter setting for address verification
+probes. This information can be overruled with the <a href="transport.5.html">transport(5)</a> table.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_sender">address_verify_sender</a>
+(default: $<a href="postconf.5.html#double_bounce_sender">double_bounce_sender</a>)</b></DT><DD>
+
+<p> The sender address to use in address verification probes; prior
+to Postfix 2.5 the default was "postmaster". To
+avoid problems with address probes that are sent in response to
+address probes, the Postfix SMTP server excludes the probe sender
+address from all SMTPD access blocks. </p>
+
+<p>
+Specify an empty value (<a href="postconf.5.html#address_verify_sender">address_verify_sender</a> =) or &lt;&gt; if you want
+to use the null sender address. Beware, some sites reject mail from
+&lt;&gt;, even though RFCs require that such addresses be accepted.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#address_verify_sender">address_verify_sender</a> = &lt;&gt;
+<a href="postconf.5.html#address_verify_sender">address_verify_sender</a> = postmaster@my.domain
+</pre>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_sender_dependent_default_transport_maps">address_verify_sender_dependent_default_transport_maps</a>
+(default: $<a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a>)</b></DT><DD>
+
+<p> Overrides the <a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a> parameter
+setting for address verification probes. </p>
+
+<p> This feature is available in Postfix 2.7 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_sender_dependent_relayhost_maps">address_verify_sender_dependent_relayhost_maps</a>
+(default: $<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>)</b></DT><DD>
+
+<p>
+Overrides the <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> parameter setting for address
+verification probes.
+</p>
+
+<p>
+This feature is available in Postfix 2.3 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_sender_ttl">address_verify_sender_ttl</a>
+(default: 0s)</b></DT><DD>
+
+<p> The time between changes in the time-dependent portion of address
+verification probe sender addresses. The time-dependent portion is
+appended to the localpart of the address specified with the
+<a href="postconf.5.html#address_verify_sender">address_verify_sender</a> parameter. This feature is ignored when the
+probe sender addresses is the null sender, i.e. the <a href="postconf.5.html#address_verify_sender">address_verify_sender</a>
+value is empty or &lt;&gt;. </p>
+
+<p> Historically, the probe sender address was fixed. This has
+caused such addresses to end up on spammer mailing lists, and has
+resulted in wasted network and processing resources. </p>
+
+<p> To enable time-dependent probe sender addresses, specify a
+non-zero time value (an integral value plus an optional one-letter
+suffix that specifies the time unit). Specify a value of at least
+several hours, to avoid problems with senders that use greylisting.
+Avoid nice TTL values, to make the result less predictable. Time
+units are: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+</p>
+
+<p> This feature is available in Postfix 2.9 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_service_name">address_verify_service_name</a>
+(default: verify)</b></DT><DD>
+
+<p>
+The name of the <a href="verify.8.html">verify(8)</a> address verification service. This service
+maintains the status of sender and/or recipient address verification
+probes, and generates probes on request by other Postfix processes.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_transport_maps">address_verify_transport_maps</a>
+(default: $<a href="postconf.5.html#transport_maps">transport_maps</a>)</b></DT><DD>
+
+<p>
+Overrides the <a href="postconf.5.html#transport_maps">transport_maps</a> parameter setting for address verification
+probes.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="address_verify_virtual_transport">address_verify_virtual_transport</a>
+(default: $<a href="postconf.5.html#virtual_transport">virtual_transport</a>)</b></DT><DD>
+
+<p>
+Overrides the <a href="postconf.5.html#virtual_transport">virtual_transport</a> parameter setting for address
+verification probes.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="alias_database">alias_database</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The alias databases for <a href="local.8.html">local(8)</a> delivery that are updated with
+"<b>newaliases</b>" or with "<b>sendmail -bi</b>".
+</p>
+
+<p>
+This is a separate configuration parameter because not all the
+tables specified with $<a href="postconf.5.html#alias_maps">alias_maps</a> have to be local files.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#alias_database">alias_database</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/aliases
+<a href="postconf.5.html#alias_database">alias_database</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/mail/aliases
+</pre>
+
+
+</DD>
+
+<DT><b><a name="alias_maps">alias_maps</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The alias databases that are used for <a href="local.8.html">local(8)</a> delivery. See
+<a href="aliases.5.html">aliases(5)</a> for syntax details.
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+Note: these lookups are recursive.
+</p>
+
+<p>
+The default list is system dependent. On systems with NIS, the
+default is to search the local alias database, then the NIS alias
+database.
+</p>
+
+<p>
+If you change the alias database, run "<b>postalias /etc/aliases</b>"
+(or wherever your system stores the mail alias file), or simply
+run "<b>newaliases</b>" to build the necessary DBM or DB file.
+</p>
+
+<p>
+The <a href="local.8.html">local(8)</a> delivery agent disallows regular expression substitution
+of $1 etc. in <a href="postconf.5.html#alias_maps">alias_maps</a>, because that would open a security hole.
+</p>
+
+<p>
+The <a href="local.8.html">local(8)</a> delivery agent will silently ignore requests to use
+the <a href="proxymap.8.html">proxymap(8)</a> server within <a href="postconf.5.html#alias_maps">alias_maps</a>. Instead it will open the
+table directly. Before Postfix version 2.2, the <a href="local.8.html">local(8)</a> delivery
+agent will terminate with a fatal error.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#alias_maps">alias_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/aliases, nis:mail.aliases
+<a href="postconf.5.html#alias_maps">alias_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/aliases
+</pre>
+
+
+</DD>
+
+<DT><b><a name="allow_mail_to_commands">allow_mail_to_commands</a>
+(default: alias, forward)</b></DT><DD>
+
+<p>
+Restrict <a href="local.8.html">local(8)</a> mail delivery to external commands. The default
+is to disallow delivery to "|command" in :include: files (see
+<a href="aliases.5.html">aliases(5)</a> for the text that defines this terminology).
+</p>
+
+<p>
+Specify zero or more of: <b>alias</b>, <b>forward</b> or <b>include</b>,
+in order to allow commands in <a href="aliases.5.html">aliases(5)</a>, .forward files or in
+:include: files, respectively.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#allow_mail_to_commands">allow_mail_to_commands</a> = alias,forward,include
+</pre>
+
+
+</DD>
+
+<DT><b><a name="allow_mail_to_files">allow_mail_to_files</a>
+(default: alias, forward)</b></DT><DD>
+
+<p>
+Restrict <a href="local.8.html">local(8)</a> mail delivery to external files. The default is
+to disallow "/file/name" destinations in :include: files (see
+<a href="aliases.5.html">aliases(5)</a> for the text that defines this terminology).
+</p>
+
+<p>
+Specify zero or more of: <b>alias</b>, <b>forward</b> or <b>include</b>,
+in order to allow "/file/name" destinations in <a href="aliases.5.html">aliases(5)</a>, .forward
+files and in :include: files, respectively.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#allow_mail_to_files">allow_mail_to_files</a> = alias,forward,include
+</pre>
+
+
+</DD>
+
+<DT><b><a name="allow_min_user">allow_min_user</a>
+(default: no)</b></DT><DD>
+
+<p>
+Allow a sender or recipient address to have `-' as the first
+character. By
+default, this is not allowed, to avoid accidents with software that
+passes email addresses via the command line. Such software
+would not be able to distinguish a malicious address from a
+bona fide command-line option. Although this can be prevented by
+inserting a "--" option terminator into the command line, this is
+difficult to enforce consistently and globally. </p>
+
+<p> As of Postfix version 2.5, this feature is implemented by
+<a href="trivial-rewrite.8.html">trivial-rewrite(8)</a>. With earlier versions this feature was implemented
+by <a href="qmgr.8.html">qmgr(8)</a> and was limited to recipient addresses only. </p>
+
+
+</DD>
+
+<DT><b><a name="allow_percent_hack">allow_percent_hack</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Enable the rewriting of the form "user%domain" to "user@domain".
+This is enabled by default.
+</p>
+
+<p> Note: as of Postfix version 2.2, message header address rewriting
+happens only when one of the following conditions is true: </p>
+
+<ul>
+
+<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,
+
+<li> The message is received from a network client that matches
+$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,
+
+<li> The message is received from the network, and the
+<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.
+
+</ul>
+
+<p> To get the behavior before Postfix version 2.2, specify
+"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all". </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#allow_percent_hack">allow_percent_hack</a> = no
+</pre>
+
+
+</DD>
+
+<DT><b><a name="allow_untrusted_routing">allow_untrusted_routing</a>
+(default: no)</b></DT><DD>
+
+<p>
+Forward mail with sender-specified routing (user[@%!]remote[@%!]site)
+from untrusted clients to destinations matching $<a href="postconf.5.html#relay_domains">relay_domains</a>.
+</p>
+
+<p>
+By default, this feature is turned off. This closes a nasty open
+relay loophole where a backup MX host can be tricked into forwarding
+junk mail to a primary MX host which then spams it out to the world.
+</p>
+
+<p>
+This parameter also controls if non-local addresses with sender-specified
+routing can match Postfix access tables. By default, such addresses
+cannot match Postfix access tables, because the address is ambiguous.
+</p>
+
+
+</DD>
+
+<DT><b><a name="alternate_config_directories">alternate_config_directories</a>
+(default: empty)</b></DT><DD>
+
+<p>
+A list of non-default Postfix configuration directories that may
+be specified with "-c <a href="postconf.5.html#config_directory">config_directory</a>" on the command line (in the
+case of <a href="sendmail.1.html">sendmail(1)</a>, with the "-C" option), or via the MAIL_CONFIG
+environment parameter.
+</p>
+
+<p>
+This list must be specified in the default Postfix <a href="postconf.5.html">main.cf</a> file,
+and will be used by set-gid Postfix commands such as <a href="postqueue.1.html">postqueue(1)</a>
+and <a href="postdrop.1.html">postdrop(1)</a>.
+</p>
+
+<p>
+Specify absolute pathnames, separated by comma or space. Note: $name
+expansion is not supported.
+</p>
+
+
+</DD>
+
+<DT><b><a name="always_add_missing_headers">always_add_missing_headers</a>
+(default: no)</b></DT><DD>
+
+<p> Always add (Resent-) From:, To:, Date: or Message-ID: headers
+when not present. Postfix 2.6 and later add these headers only
+when clients match the <a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> parameter
+setting. Earlier Postfix versions always add these headers; this
+may break DKIM signatures that cover non-existent headers.
+The <a href="postconf.5.html#undisclosed_recipients_header">undisclosed_recipients_header</a> parameter setting determines
+whether a To: header will be added. </p>
+
+
+</DD>
+
+<DT><b><a name="always_bcc">always_bcc</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional address that receives a "blind carbon copy" of each message
+that is received by the Postfix mail system.
+</p>
+
+<p>
+Note: with Postfix 2.3 and later the BCC address is added as if it
+was specified with NOTIFY=NONE. The sender will not be notified
+when the BCC address is undeliverable, as long as all down-stream
+software implements <a href="http://tools.ietf.org/html/rfc3461">RFC 3461</a>.
+</p>
+
+<p>
+Note: with Postfix 2.2 and earlier the sender will be notified
+when the BCC address is undeliverable.
+</p>
+
+<p> Note: automatic BCC recipients are produced only for new mail.
+To avoid mailer loops, automatic BCC recipients are not generated
+after Postfix forwards mail internally, or after Postfix generates
+mail itself. </p>
+
+
+</DD>
+
+<DT><b><a name="anvil_rate_time_unit">anvil_rate_time_unit</a>
+(default: 60s)</b></DT><DD>
+
+<p>
+The time unit over which client connection rates and other rates
+are calculated.
+</p>
+
+<p>
+This feature is implemented by the <a href="anvil.8.html">anvil(8)</a> service which is available
+in Postfix version 2.2 and later.
+</p>
+
+<p>
+The default interval is relatively short. Because of the high
+frequency of updates, the <a href="anvil.8.html">anvil(8)</a> server uses volatile memory
+only. Thus, information is lost whenever the process terminates.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="anvil_status_update_time">anvil_status_update_time</a>
+(default: 600s)</b></DT><DD>
+
+<p>
+How frequently the <a href="anvil.8.html">anvil(8)</a> connection and rate limiting server
+logs peak usage information.
+</p>
+
+<p>
+This feature is available in Postfix 2.2 and later.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="append_at_myorigin">append_at_myorigin</a>
+(default: yes)</b></DT><DD>
+
+<p>
+With locally submitted mail, append the string "@$<a href="postconf.5.html#myorigin">myorigin</a>" to mail
+addresses without domain information. With remotely submitted mail,
+append the string "@$<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a>" instead.
+</p>
+
+<p>
+Note 1: this feature is enabled by default and must not be turned off.
+Postfix does not support domain-less addresses.
+</p>
+
+<p> Note 2: with Postfix version 2.2, message header address rewriting
+happens only when one of the following conditions is true: </p>
+
+<ul>
+
+<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,
+
+<li> The message is received from a network client that matches
+$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,
+
+<li> The message is received from the network, and the
+<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.
+
+</ul>
+
+<p> To get the behavior before Postfix version 2.2, specify
+"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all". </p>
+
+
+</DD>
+
+<DT><b><a name="append_dot_mydomain">append_dot_mydomain</a>
+(default: Postfix &ge; 3.0: no, Postfix &lt; 3.0: yes)</b></DT><DD>
+
+<p>
+With locally submitted mail, append the string ".$<a href="postconf.5.html#mydomain">mydomain</a>" to
+addresses that have no ".domain" information. With remotely submitted
+mail, append the string ".$<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a>"
+instead.
+</p>
+
+<p>
+Note 1: this feature is enabled by default. If disabled, users will not be
+able to send mail to "user@partialdomainname" but will have to
+specify full domain names instead.
+</p>
+
+<p> Note 2: with Postfix version 2.2, message header address rewriting
+happens only when one of the following conditions is true: </p>
+
+<ul>
+
+<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,
+
+<li> The message is received from a network client that matches
+$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,
+
+<li> The message is received from the network, and the
+<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.
+
+</ul>
+
+<p> To get the behavior before Postfix version 2.2, specify
+"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all". </p>
+
+
+</DD>
+
+<DT><b><a name="application_event_drain_time">application_event_drain_time</a>
+(default: 100s)</b></DT><DD>
+
+<p>
+How long the <a href="postkick.1.html">postkick(1)</a> command waits for a request to enter the
+Postfix daemon process input buffer before giving up.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="authorized_flush_users">authorized_flush_users</a>
+(default: <a href="DATABASE_README.html#types">static</a>:anyone)</b></DT><DD>
+
+<p>
+List of users who are authorized to flush the queue.
+</p>
+
+<p>
+By default, all users are allowed to flush the queue. Access is
+always granted if the invoking user is the super-user or the
+$<a href="postconf.5.html#mail_owner">mail_owner</a> user. Otherwise, the real UID of the process is looked
+up in the system password file, and access is granted only if the
+corresponding login name is on the access list. The username
+"unknown" is used for processes whose real UID is not found in the
+password file. </p>
+
+<p>
+Specify a list of user names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns,
+separated by commas and/or whitespace. The list is matched left to
+right, and the search stops on the first match. A "/file/name"
+pattern is replaced
+by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name
+matches a lookup key (the lookup result is ignored). Continue long
+lines by starting the next line with whitespace. Specify "!pattern"
+to exclude a name from the list. The form "!/file/name" is supported
+only in Postfix version 2.4 and later. </p>
+
+<p>
+This feature is available in Postfix 2.2 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="authorized_mailq_users">authorized_mailq_users</a>
+(default: <a href="DATABASE_README.html#types">static</a>:anyone)</b></DT><DD>
+
+<p>
+List of users who are authorized to view the queue.
+</p>
+
+<p>
+By default, all users are allowed to view the queue. Access is
+always granted if the invoking user is the super-user or the
+$<a href="postconf.5.html#mail_owner">mail_owner</a> user. Otherwise, the real UID of the process is looked
+up in the system password file, and access is granted only if the
+corresponding login name is on the access list. The username
+"unknown" is used for processes whose real UID is not found in the
+password file. </p>
+
+<p>
+Specify a list of user names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns,
+separated by commas and/or whitespace. The list is matched left to
+right, and the search stops on the first match. A "/file/name"
+pattern is replaced
+by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name
+matches a lookup key (the lookup result is ignored). Continue long
+lines by starting the next line with whitespace. Specify "!pattern"
+to exclude a user name from the list. The form "!/file/name" is
+supported only in Postfix version 2.4 and later. </p>
+
+<p>
+This feature is available in Postfix 2.2 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="authorized_submit_users">authorized_submit_users</a>
+(default: <a href="DATABASE_README.html#types">static</a>:anyone)</b></DT><DD>
+
+<p>
+List of users who are authorized to submit mail with the <a href="sendmail.1.html">sendmail(1)</a>
+command (and with the privileged <a href="postdrop.1.html">postdrop(1)</a> helper command).
+</p>
+
+<p>
+By default, all users are allowed to submit mail. Otherwise, the
+real UID of the process is looked up in the system password file,
+and access is granted only if the corresponding login name is on
+the access list. The username "unknown" is used for processes
+whose real UID is not found in the password file. To deny mail
+submission access to all users specify an empty list. </p>
+
+<p>
+Specify a list of user names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns,
+separated by commas and/or whitespace. The list is matched left to right,
+and the search stops on the first match. A "/file/name" pattern is
+replaced by its contents;
+a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name matches a lookup key
+(the lookup result is ignored). Continue long lines by starting the
+next line with whitespace. Specify "!pattern" to exclude a user
+name from the list. The form "!/file/name" is supported only in
+Postfix version 2.4 and later. </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#authorized_submit_users">authorized_submit_users</a> = !www, <a href="DATABASE_README.html#types">static</a>:all
+</pre>
+
+<p>
+This feature is available in Postfix 2.2 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="authorized_verp_clients">authorized_verp_clients</a>
+(default: $<a href="postconf.5.html#mynetworks">mynetworks</a>)</b></DT><DD>
+
+<p> What remote SMTP clients are allowed to specify the XVERP command.
+This command requests that mail be delivered one recipient at a
+time with a per recipient return address. </p>
+
+<p> By default, only trusted clients are allowed to specify XVERP.
+</p>
+
+<p> This parameter was introduced with Postfix version 1.1. Postfix
+version 2.1 renamed this parameter to <a href="postconf.5.html#smtpd_authorized_verp_clients">smtpd_authorized_verp_clients</a>
+and changed the default to none. </p>
+
+<p> Specify a list of network/netmask patterns, separated by commas
+and/or whitespace. The mask specifies the number of bits in the
+network part of a host address. You can also specify hostnames or
+.domain names (the initial dot causes the domain to match any name
+below it), "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns. A "/file/name"
+pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table
+is matched when a table entry matches a lookup string (the lookup
+result is ignored). Continue long lines by starting the next line
+with whitespace. Specify "!pattern" to exclude an address or network
+block from the list. The form "!/file/name" is supported only in
+Postfix version 2.4 and later. </p>
+
+<p> Note: IP version 6 address information must be specified inside
+<tt>[]</tt> in the <a href="postconf.5.html#authorized_verp_clients">authorized_verp_clients</a> value, and in files
+specified with "/file/name". IP version 6 addresses contain the
+":" character, and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>"
+pattern. </p>
+
+
+</DD>
+
+<DT><b><a name="backwards_bounce_logfile_compatibility">backwards_bounce_logfile_compatibility</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Produce additional <a href="bounce.8.html">bounce(8)</a> logfile records that can be read by
+Postfix versions before 2.0. The current and more extensible "name =
+value" format is needed in order to implement more sophisticated
+functionality.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="berkeley_db_create_buffer_size">berkeley_db_create_buffer_size</a>
+(default: 16777216)</b></DT><DD>
+
+<p>
+The per-table I/O buffer size for programs that create Berkeley DB
+hash or btree tables. Specify a byte count.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="berkeley_db_read_buffer_size">berkeley_db_read_buffer_size</a>
+(default: 131072)</b></DT><DD>
+
+<p>
+The per-table I/O buffer size for programs that read Berkeley DB
+hash or btree tables. Specify a byte count.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="best_mx_transport">best_mx_transport</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Where the Postfix SMTP client should deliver mail when it detects
+a "mail loops back to myself" error condition. This happens when
+the local MTA is the best SMTP mail exchanger for a destination
+not listed in $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>, $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>,
+$<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, or $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>. By default,
+the Postfix SMTP client returns such mail as undeliverable.
+</p>
+
+<p>
+Specify, for example, "<a href="postconf.5.html#best_mx_transport">best_mx_transport</a> = local" to pass the mail
+from the Postfix SMTP client to the <a href="local.8.html">local(8)</a> delivery agent. You
+can specify
+any message delivery "transport" or "transport:nexthop" that is
+defined in the <a href="master.5.html">master.cf</a> file. See the <a href="transport.5.html">transport(5)</a> manual page
+for the syntax and meaning of "transport" or "transport:nexthop".
+</p>
+
+<p>
+However, this feature is expensive because it ties up a Postfix
+SMTP client process while the <a href="local.8.html">local(8)</a> delivery agent is doing its
+work. It is more efficient (for Postfix) to list all <a href="VIRTUAL_README.html#canonical">hosted domains</a>
+in a table or database.
+</p>
+
+
+</DD>
+
+<DT><b><a name="biff">biff</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Whether or not to use the local <a href="postconf.5.html#biff">biff</a> service. This service sends
+"new mail" notifications to users who have requested new mail
+notification with the UNIX command "<a href="postconf.5.html#biff">biff</a> y".
+</p>
+
+<p>
+For compatibility reasons this feature is on by default. On systems
+with lots of interactive users, the <a href="postconf.5.html#biff">biff</a> service can be a performance
+drain. Specify "<a href="postconf.5.html#biff">biff</a> = no" in <a href="postconf.5.html">main.cf</a> to disable.
+</p>
+
+
+</DD>
+
+<DT><b><a name="body_checks">body_checks</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional lookup tables for content inspection as specified in
+the <a href="header_checks.5.html">body_checks(5)</a> manual page. </p>
+
+<p> Note: with Postfix versions before 2.0, these rules inspect
+all content after the primary message headers. </p>
+
+
+</DD>
+
+<DT><b><a name="body_checks_size_limit">body_checks_size_limit</a>
+(default: 51200)</b></DT><DD>
+
+<p>
+How much text in a message body segment (or attachment, if you
+prefer to use that term) is subjected to <a href="postconf.5.html#body_checks">body_checks</a> inspection.
+The amount of text is limited to avoid scanning huge attachments.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="bounce_notice_recipient">bounce_notice_recipient</a>
+(default: postmaster)</b></DT><DD>
+
+<p>
+The recipient of postmaster notifications with the message headers
+of mail that Postfix did not deliver and of SMTP conversation
+transcripts of mail that Postfix did not receive. This feature is
+enabled with the <a href="postconf.5.html#notify_classes">notify_classes</a> parameter. </p>
+
+
+</DD>
+
+<DT><b><a name="bounce_queue_lifetime">bounce_queue_lifetime</a>
+(default: 5d)</b></DT><DD>
+
+<p>
+Consider a bounce message as undeliverable, when delivery fails
+with a temporary error, and the time in the queue has reached the
+<a href="postconf.5.html#bounce_queue_lifetime">bounce_queue_lifetime</a> limit. By default, this limit is the same
+as for regular mail.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is d (days).
+</p>
+
+<p>
+Specify 0 when mail delivery should be tried only once.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="bounce_service_name">bounce_service_name</a>
+(default: bounce)</b></DT><DD>
+
+<p>
+The name of the <a href="bounce.8.html">bounce(8)</a> service. This service maintains a record
+of failed delivery attempts and generates non-delivery notifications.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="bounce_size_limit">bounce_size_limit</a>
+(default: 50000)</b></DT><DD>
+
+<p> The maximal amount of original message text that is sent in a
+non-delivery notification. Specify a byte count. A message is
+returned as either message/rfc822 (the complete original) or as
+text/rfc822-headers (the headers only). With Postfix version 2.4
+and earlier, a message is always returned as message/rfc822 and is
+truncated when it exceeds the size limit.
+</p>
+
+<p> Notes: </p>
+
+<ul>
+
+<li> <p> If you increase this limit, then you should increase the
+<a href="postconf.5.html#mime_nesting_limit">mime_nesting_limit</a> value proportionally. </p>
+
+<li> <p> Be careful when making changes. Excessively large values
+will result in the loss of non-delivery notifications, when a bounce
+message size exceeds a local or remote MTA's message size limit.
+</p>
+
+</ul>
+
+
+</DD>
+
+<DT><b><a name="bounce_template_file">bounce_template_file</a>
+(default: empty)</b></DT><DD>
+
+<p> Pathname of a configuration file with bounce message templates.
+These override the built-in templates of delivery status notification
+(DSN) messages for undeliverable mail, for delayed mail, successful
+delivery, or delivery verification. The <a href="bounce.5.html">bounce(5)</a> manual page
+describes how to edit and test template files. </p>
+
+<p> Template message body text may contain $name references to
+Postfix configuration parameters. The result of $name expansion can
+be previewed with "<b>postconf -b <i>file_name</i></b>" before the file
+is placed into the Postfix configuration directory. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="broken_sasl_auth_clients">broken_sasl_auth_clients</a>
+(default: no)</b></DT><DD>
+
+<p>
+Enable interoperability with remote SMTP clients that implement an obsolete
+version of the AUTH command (<a href="http://tools.ietf.org/html/rfc4954">RFC 4954</a>). Examples of such clients
+are MicroSoft Outlook Express version 4 and MicroSoft Exchange
+version 5.0.
+</p>
+
+<p>
+Specify "<a href="postconf.5.html#broken_sasl_auth_clients">broken_sasl_auth_clients</a> = yes" to have Postfix advertise
+AUTH support in a non-standard way.
+</p>
+
+
+</DD>
+
+<DT><b><a name="canonical_classes">canonical_classes</a>
+(default: envelope_sender, envelope_recipient, header_sender, header_recipient)</b></DT><DD>
+
+<p> What addresses are subject to <a href="postconf.5.html#canonical_maps">canonical_maps</a> address mapping.
+By default, <a href="postconf.5.html#canonical_maps">canonical_maps</a> address mapping is applied to envelope
+sender and recipient addresses, and to header sender and header
+recipient addresses. </p>
+
+<p> Specify one or more of: envelope_sender, envelope_recipient,
+header_sender, header_recipient </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="canonical_maps">canonical_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional address mapping lookup tables for message headers and
+envelopes. The mapping is applied to both sender and recipient
+addresses, in both envelopes and in headers, as controlled
+with the <a href="postconf.5.html#canonical_classes">canonical_classes</a> parameter. This is typically used
+to clean up dirty addresses from legacy mail systems, or to replace
+login names by Firstname.Lastname. The table format and lookups
+are documented in <a href="canonical.5.html">canonical(5)</a>. For an overview of Postfix address
+manipulations see the <a href="ADDRESS_REWRITING_README.html">ADDRESS_REWRITING_README</a> document.
+</p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+Note: these lookups are recursive.
+</p>
+
+<p>
+If you use this feature, run "<b>postmap /etc/postfix/canonical</b>" to
+build the necessary DBM or DB file after every change. The changes
+will become visible after a minute or so. Use "<b>postfix reload</b>"
+to eliminate the delay.
+</p>
+
+<p> Note: with Postfix version 2.2, message header address mapping
+happens only when message header address rewriting is enabled: </p>
+
+<ul>
+
+<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,
+
+<li> The message is received from a network client that matches
+$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,
+
+<li> The message is received from the network, and the
+<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.
+
+</ul>
+
+<p> To get the behavior before Postfix version 2.2, specify
+"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all". </p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#canonical_maps">canonical_maps</a> = <a href="DATABASE_README.html#types">dbm</a>:/etc/postfix/canonical
+<a href="postconf.5.html#canonical_maps">canonical_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/canonical
+</pre>
+
+
+</DD>
+
+<DT><b><a name="cleanup_service_name">cleanup_service_name</a>
+(default: cleanup)</b></DT><DD>
+
+<p>
+The name of the <a href="cleanup.8.html">cleanup(8)</a> service. This service rewrites addresses
+into the standard form, and performs <a href="canonical.5.html">canonical(5)</a> address mapping
+and <a href="virtual.5.html">virtual(5)</a> aliasing.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="command_directory">command_directory</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The location of all postfix administrative commands.
+</p>
+
+
+</DD>
+
+<DT><b><a name="command_execution_directory">command_execution_directory</a>
+(default: empty)</b></DT><DD>
+
+<p> The <a href="local.8.html">local(8)</a> delivery agent working directory for delivery to
+external command. Failure to change directory causes the delivery
+to be deferred. </p>
+
+<p> The <a href="postconf.5.html#command_execution_directory">command_execution_directory</a> value is not subject to Postfix
+configuration parameter $name expansion. Instead, the following
+$name expansions are done on <a href="postconf.5.html#command_execution_directory">command_execution_directory</a> before the
+directory is used. Expansion happens in the context
+of the delivery request. The result of $name expansion is filtered
+with the character set that is specified with the
+<a href="postconf.5.html#execution_directory_expansion_filter">execution_directory_expansion_filter</a> parameter. </p>
+
+<dl>
+
+<dt><b>$user</b></dt>
+
+<dd>The recipient's username. </dd>
+
+<dt><b>$shell</b></dt>
+
+<dd>The recipient's login shell pathname. </dd>
+
+<dt><b>$home</b></dt>
+
+<dd>The recipient's home directory. </dd>
+
+<dt><b>$recipient</b></dt>
+
+<dd>The full recipient address. </dd>
+
+<dt><b>$extension</b></dt>
+
+<dd>The optional recipient address extension. </dd>
+
+<dt><b>$domain</b></dt>
+
+<dd>The recipient domain. </dd>
+
+<dt><b>$local</b></dt>
+
+<dd>The entire recipient localpart. </dd>
+
+<dt><b>$<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a></b></dt>
+
+<dd>The address extension delimiter that was found in the recipient
+address (Postfix 2.11 and later), or the system-wide recipient
+address extension delimiter (Postfix 2.10 and earlier). </dd>
+
+<dt><b>${name?value}</b></dt>
+
+<dd>Expands to <i>value</i> when <i>$name</i> is non-empty. </dd>
+
+<dt><b>${name:value}</b></dt>
+
+<dd>Expands to <i>value</i> when <i>$name</i> is empty. </dd>
+
+</dl>
+
+<p>
+Instead of $name you can also specify ${name} or $(name).
+</p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="command_expansion_filter">command_expansion_filter</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+Restrict the characters that the <a href="local.8.html">local(8)</a> delivery agent allows in
+$name expansions of $<a href="postconf.5.html#mailbox_command">mailbox_command</a> and $<a href="postconf.5.html#command_execution_directory">command_execution_directory</a>.
+Characters outside the
+allowed set are replaced by underscores.
+</p>
+
+
+</DD>
+
+<DT><b><a name="command_time_limit">command_time_limit</a>
+(default: 1000s)</b></DT><DD>
+
+<p>
+Time limit for delivery to external commands. This limit is used
+by the <a href="local.8.html">local(8)</a> delivery agent, and is the default time limit for
+delivery by the <a href="pipe.8.html">pipe(8)</a> delivery agent.
+</p>
+
+<p>
+Note: if you set this time limit to a large value you must update the
+global <a href="postconf.5.html#ipc_timeout">ipc_timeout</a> parameter as well.
+</p>
+
+
+</DD>
+
+<DT><b><a name="compatibility_level">compatibility_level</a>
+(default: 0)</b></DT><DD>
+
+<p> A safety net that causes Postfix to run with backwards-compatible
+default settings after an upgrade to a newer Postfix version. </p>
+
+<p> With backwards compatibility turned on (the <a href="postconf.5.html">main.cf</a> <a href="postconf.5.html#compatibility_level">compatibility_level</a>
+value is less than the Postfix built-in value), Postfix looks for
+settings that are left at their implicit default value, and logs a
+message when a backwards-compatible default setting is required.
+</p>
+
+<blockquote>
+<pre>
+using backwards-compatible default setting <i>name=value</i>
+ to [accept a specific client request]
+
+using backwards-compatible default setting <i>name=value</i>
+ to [enable specific Postfix behavior]
+</pre>
+</blockquote>
+
+<p> See <a href="COMPATIBILITY_README.html">COMPATIBILITY_README</a> for specific message details. If such
+a message is logged in the context of a legitimate request, the
+system administrator should make the backwards-compatible setting
+permanent in <a href="postconf.5.html">main.cf</a> or <a href="master.5.html">master.cf</a>, for example: </p>
+
+<blockquote>
+<pre>
+# <b>postconf</b> <i>name=value</i>
+# <b>postfix reload</b>
+</pre>
+</blockquote>
+
+<p> When no more backwards-compatible settings need to be made
+permanent, the administrator should turn off backwards compatibility
+by updating the <a href="postconf.5.html#compatibility_level">compatibility_level</a> setting in <a href="postconf.5.html">main.cf</a>:</p>
+
+<blockquote>
+<pre>
+# <b>postconf <a href="postconf.5.html#compatibility_level">compatibility_level</a>=<i>N</i></b>
+# <b>postfix reload</b>
+</pre>
+</blockquote>
+
+<p> For <i>N</i> specify the number that is logged in your <a href="postfix.1.html">postfix(1)</a>
+warning message: </p>
+
+<blockquote>
+<pre>
+warning: To disable backwards compatibility use "postconf
+ <a href="postconf.5.html#compatibility_level">compatibility_level</a>=<i>N</i>" and "postfix reload"
+</pre>
+</blockquote>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="config_directory">config_directory</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The default location of the Postfix <a href="postconf.5.html">main.cf</a> and <a href="master.5.html">master.cf</a>
+configuration files. This can be overruled via the following
+mechanisms: </p>
+
+<ul>
+
+<li> <p> The MAIL_CONFIG environment variable (daemon processes
+and commands). </p>
+
+<li> <p> The "-c" command-line option (commands only). </p>
+
+</ul>
+
+<p> With Postfix command that run with set-gid privileges, a
+<a href="postconf.5.html#config_directory">config_directory</a> override requires either root privileges, or it
+requires that the directory is listed with the <a href="postconf.5.html#alternate_config_directories">alternate_config_directories</a>
+parameter in the default <a href="postconf.5.html">main.cf</a> file. </p>
+
+
+</DD>
+
+<DT><b><a name="confirm_delay_cleared">confirm_delay_cleared</a>
+(default: no)</b></DT><DD>
+
+<p> After sending a "your message is delayed" notification, inform
+the sender when the delay clears up. This can result in a sudden
+burst of notifications at the end of a prolonged network outage,
+and is therefore disabled by default. </p>
+
+<p> See also: <a href="postconf.5.html#delay_warning_time">delay_warning_time</a>. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="connection_cache_protocol_timeout">connection_cache_protocol_timeout</a>
+(default: 5s)</b></DT><DD>
+
+<p> Time limit for connection cache connect, send or receive
+operations. The time limit is enforced in the client. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="connection_cache_service_name">connection_cache_service_name</a>
+(default: scache)</b></DT><DD>
+
+<p> The name of the <a href="scache.8.html">scache(8)</a> connection cache service. This service
+maintains a limited pool of cached sessions. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="connection_cache_status_update_time">connection_cache_status_update_time</a>
+(default: 600s)</b></DT><DD>
+
+<p> How frequently the <a href="scache.8.html">scache(8)</a> server logs usage statistics with
+connection cache hit and miss rates for logical destinations and for
+physical endpoints. </p>
+
+
+</DD>
+
+<DT><b><a name="connection_cache_ttl_limit">connection_cache_ttl_limit</a>
+(default: 2s)</b></DT><DD>
+
+<p> The maximal time-to-live value that the <a href="scache.8.html">scache(8)</a> connection
+cache server
+allows. Requests that specify a larger TTL will be stored with the
+maximum allowed TTL. The purpose of this additional control is to
+protect the infrastructure against careless people. The cache TTL
+is already bounded by $<a href="postconf.5.html#max_idle">max_idle</a>. </p>
+
+
+</DD>
+
+<DT><b><a name="content_filter">content_filter</a>
+(default: empty)</b></DT><DD>
+
+<p> After the message is queued, send the entire message to the
+specified <i>transport:destination</i>. The <i>transport</i> name
+specifies the first field of a mail delivery agent definition in
+<a href="master.5.html">master.cf</a>; the syntax of the next-hop <i>destination</i> is described
+in the manual page of the corresponding delivery agent. More
+information about external content filters is in the Postfix
+<a href="FILTER_README.html">FILTER_README</a> file. </p>
+
+<p> Notes: </p>
+
+<ul>
+
+<li> <p> This setting has lower precedence than a FILTER action
+that is specified in an <a href="access.5.html">access(5)</a>, <a href="header_checks.5.html">header_checks(5)</a> or <a href="header_checks.5.html">body_checks(5)</a>
+table. </p>
+
+<li> <p> The meaning of an empty next-hop filter <i>destination</i>
+is version dependent. Postfix 2.7 and later will use the recipient
+domain; earlier versions will use $<a href="postconf.5.html#myhostname">myhostname</a>. Specify
+"<a href="postconf.5.html#default_filter_nexthop">default_filter_nexthop</a> = $<a href="postconf.5.html#myhostname">myhostname</a>" for compatibility with Postfix
+2.6 or earlier, or specify a <a href="postconf.5.html#content_filter">content_filter</a> value with an explicit
+next-hop <i>destination</i>. </p>
+
+</ul>
+
+
+</DD>
+
+<DT><b><a name="cyrus_sasl_config_path">cyrus_sasl_config_path</a>
+(default: empty)</b></DT><DD>
+
+<p> Search path for Cyrus SASL application configuration files,
+currently used only to locate the $<a href="postconf.5.html#smtpd_sasl_path">smtpd_sasl_path</a>.conf file.
+Specify zero or more directories separated by a colon character,
+or an empty value to use Cyrus SASL's built-in search path. </p>
+
+<p> This feature is available in Postfix 2.5 and later when compiled
+with Cyrus SASL 2.1.22 or later. </p>
+
+
+</DD>
+
+<DT><b><a name="daemon_directory">daemon_directory</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The directory with Postfix support programs and daemon programs.
+These should not be invoked directly by humans. The directory must
+be owned by root.
+</p>
+
+
+</DD>
+
+<DT><b><a name="daemon_table_open_error_is_fatal">daemon_table_open_error_is_fatal</a>
+(default: no)</b></DT><DD>
+
+<p> How a Postfix daemon process handles errors while opening lookup
+tables: gradual degradation or immediate termination. </p>
+
+<dl>
+
+<dt> <b> no </b> (default) </dt> <dd> <p> Gradual degradation: a
+daemon process logs a message of type "error" and continues execution
+with reduced functionality. Features that do not depend on the
+unavailable table will work normally, while features that depend
+on the table will result in a type "warning" message. <br> When
+the <a href="postconf.5.html#notify_classes">notify_classes</a> parameter value contains the "data" class, the
+Postfix SMTP server and client will report transcripts of sessions
+with an error because a table is unavailable. </p> </dd>
+
+<dt> <b> yes </b> (historical behavior) </dt> <dd> <p> Immediate
+termination: a daemon process logs a type "fatal" message and
+terminates immediately. This option reduces the number of possible
+code paths through Postfix, and may therefore be slightly more
+secure than the default. </p> </dd>
+
+</dl>
+
+<p> For the sake of sanity, the number of type "error" messages is
+limited to 13 over the lifetime of a daemon process. </p>
+
+<p> This feature is available in Postfix 2.9 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="daemon_timeout">daemon_timeout</a>
+(default: 18000s)</b></DT><DD>
+
+<p> How much time a Postfix daemon process may take to handle a
+request before it is terminated by a built-in watchdog timer. </p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="data_directory">data_directory</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The directory with Postfix-writable data files (for example:
+caches, pseudo-random numbers). This directory must be owned by
+the <a href="postconf.5.html#mail_owner">mail_owner</a> account, and must not be shared with non-Postfix
+software. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="debug_peer_level">debug_peer_level</a>
+(default: 2)</b></DT><DD>
+
+<p> The increment in verbose logging level when a remote client or
+server matches a pattern in the <a href="postconf.5.html#debug_peer_list">debug_peer_list</a> parameter. </p>
+
+
+</DD>
+
+<DT><b><a name="debug_peer_list">debug_peer_list</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional list of remote client or server hostname or network
+address patterns that cause the verbose logging level to increase
+by the amount specified in $<a href="postconf.5.html#debug_peer_level">debug_peer_level</a>. </p>
+
+<p> Specify domain names, network/netmask patterns, "/file/name"
+patterns or "<a href="DATABASE_README.html">type:table</a>" lookup tables. The right-hand side result
+from "<a href="DATABASE_README.html">type:table</a>" lookups is ignored. </p>
+
+<p> Pattern matching of domain names is controlled by the presence
+or absence of "<a href="postconf.5.html#debug_peer_list">debug_peer_list</a>" in the <a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a>
+parameter value. </p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#debug_peer_list">debug_peer_list</a> = 127.0.0.1
+<a href="postconf.5.html#debug_peer_list">debug_peer_list</a> = example.com
+</pre>
+
+
+</DD>
+
+<DT><b><a name="debugger_command">debugger_command</a>
+(default: empty)</b></DT><DD>
+
+<p>
+The external command to execute when a Postfix daemon program is
+invoked with the -D option.
+</p>
+
+<p>
+Use "command .. &amp; sleep 5" so that the debugger can attach before
+the process marches on. If you use an X-based debugger, be sure to
+set up your XAUTHORITY environment variable before starting Postfix.
+</p>
+
+<p>
+Note: the command is subject to $name expansion, before it is
+passed to the default command interpreter. Specify "$$" to
+produce a single "$" character.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#debugger_command">debugger_command</a> =
+ PATH=/usr/bin:/usr/X11R6/bin
+ ddd $<a href="postconf.5.html#daemon_directory">daemon_directory</a>/$<a href="postconf.5.html#process_name">process_name</a> $<a href="postconf.5.html#process_id">process_id</a> &amp; sleep 5
+</pre>
+
+
+</DD>
+
+<DT><b><a name="default_database_type">default_database_type</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The default database type for use in <a href="newaliases.1.html">newaliases(1)</a>, <a href="postalias.1.html">postalias(1)</a>
+and <a href="postmap.1.html">postmap(1)</a> commands. On many UNIX systems the default type is
+either <b>dbm</b> or <b>hash</b>. The default setting is frozen
+when the Postfix system is built.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#default_database_type">default_database_type</a> = hash
+<a href="postconf.5.html#default_database_type">default_database_type</a> = dbm
+</pre>
+
+
+</DD>
+
+<DT><b><a name="default_delivery_slot_cost">default_delivery_slot_cost</a>
+(default: 5)</b></DT><DD>
+
+<p>
+How often the Postfix queue manager's scheduler is allowed to
+preempt delivery of one message with another.
+</p>
+
+<p>
+Each transport maintains a so-called "available delivery slot counter"
+for each message. One message can be preempted by another one when
+the other message can be delivered using no more delivery slots
+(i.e., invocations of delivery agents) than the current message
+counter has accumulated (or will eventually accumulate - see about
+slot loans below). This parameter controls how often is the counter
+incremented - it happens after each <a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a>
+recipients have been delivered.
+</p>
+
+<p>
+The cost of 0 is used to disable the preempting scheduling completely.
+The minimum value the scheduling algorithm can use is 2 - use it
+if you want to maximize the message throughput rate. Although there
+is no maximum, it doesn't make much sense to use values above say
+50.
+</p>
+
+<p>
+The only reason why the value of 2 is not the default is the way
+this parameter affects the delivery of mailing-list mail. In the
+worst case, delivery can take somewhere between (cost+1/cost)
+and (cost/cost-1) times more than if the preemptive scheduler was
+disabled. The default value of 5 turns out to provide reasonable
+message response times while making sure the mailing-list deliveries
+are not extended by more than 20-25 percent even in the worst case.
+</p>
+
+<p> Use <a href="postconf.5.html#transport_delivery_slot_cost"><i>transport</i>_delivery_slot_cost</a> to specify a
+transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a> = 0
+<a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a> = 2
+</pre>
+
+
+</DD>
+
+<DT><b><a name="default_delivery_slot_discount">default_delivery_slot_discount</a>
+(default: 50)</b></DT><DD>
+
+<p>
+The default value for transport-specific _delivery_slot_discount
+settings.
+</p>
+
+<p>
+This parameter speeds up the moment when a message preemption can
+happen. Instead of waiting until the full amount of delivery slots
+required is available, the preemption can happen when
+transport_delivery_slot_discount percent of the required amount
+plus transport_delivery_slot_loan still remains to be accumulated.
+Note that the full amount will still have to be accumulated before
+another preemption can take place later.
+</p>
+
+<p> Use <a href="postconf.5.html#transport_delivery_slot_discount"><i>transport</i>_delivery_slot_discount</a> to specify a
+transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport.
+</p>
+
+
+</DD>
+
+<DT><b><a name="default_delivery_slot_loan">default_delivery_slot_loan</a>
+(default: 3)</b></DT><DD>
+
+<p>
+The default value for transport-specific _delivery_slot_loan
+settings.
+</p>
+
+<p>
+This parameter speeds up the moment when a message preemption can
+happen. Instead of waiting until the full amount of delivery slots
+required is available, the preemption can happen when
+transport_delivery_slot_discount percent of the required amount
+plus transport_delivery_slot_loan still remains to be accumulated.
+Note that the full amount will still have to be accumulated before
+another preemption can take place later.
+</p>
+
+<p> Use <a href="postconf.5.html#transport_delivery_slot_loan"><i>transport</i>_delivery_slot_loan</a> to specify a
+transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport.
+</p>
+
+
+</DD>
+
+<DT><b><a name="default_delivery_status_filter">default_delivery_status_filter</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional filter to replace the delivery status code or explanatory
+text of successful or unsuccessful deliveries. This does not allow
+the replacement of a successful status code (2.X.X) with an
+unsuccessful status code (4.X.X or 5.X.X) or vice versa. </p>
+
+<p> Note: the (smtp|lmtp)_delivery_status_filter is applied only
+once per recipient: when delivery is successful, when delivery is
+rejected with 5XX, or when there are no more alternate MX or A
+destinations. Use <a href="postconf.5.html#smtp_reply_filter">smtp_reply_filter</a> or <a href="postconf.5.html#lmtp_reply_filter">lmtp_reply_filter</a> to inspect
+responses for all delivery attempts. </p>
+
+<p> The following parameters can be used to implement a filter for
+specific delivery agents: <a href="postconf.5.html#lmtp_delivery_status_filter">lmtp_delivery_status_filter</a>,
+<a href="postconf.5.html#local_delivery_status_filter">local_delivery_status_filter</a>, <a href="postconf.5.html#pipe_delivery_status_filter">pipe_delivery_status_filter</a>,
+<a href="postconf.5.html#smtp_delivery_status_filter">smtp_delivery_status_filter</a> or <a href="postconf.5.html#virtual_delivery_status_filter">virtual_delivery_status_filter</a>. These
+parameters support the same filter syntax as described here. </p>
+
+<p> Specify zero or more "<a href="DATABASE_README.html">type:table</a>" lookup table names, separated
+by comma or whitespace. For each successful or unsuccessful delivery
+to a recipient, the tables are queried in the specified order with
+one line of text that is structured as follows: </p>
+
+<blockquote>
+enhanced-status-code SPACE explanatory-text
+</blockquote>
+
+<p> The first table match wins. The lookup result must have the
+same structure as the query, a successful status code (2.X.X) must
+be replaced with a successful status code, an unsuccessful status
+code (4.X.X or 5.X.X) must be replaced with an unsuccessful status
+code, and the explanatory text field must be non-empty. Other results
+will result in a warning. </p>
+
+<p> Example 1: convert specific soft TLS errors into hard errors,
+by overriding the first number in the enhanced status code. </p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtp_delivery_status_filter">smtp_delivery_status_filter</a> = <a href="pcre_table.5.html">pcre</a>:/etc/postfix/smtp_dsn_filter
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/smtp_dsn_filter:
+ /^4(\.\d+\.\d+ TLS is required, but host \S+ refused to start TLS: .+)/
+ 5$1
+ /^4(\.\d+\.\d+ TLS is required, but was not offered by host .+)/
+ 5$1
+ # Do not change the following into hard bounces. They may
+ # result from a local configuration problem.
+ # 4.\d+.\d+ TLS is required, but our TLS engine is unavailable
+ # 4.\d+.\d+ TLS is required, but unavailable
+ # 4.\d+.\d+ Cannot start TLS: handshake failure
+</pre>
+</blockquote>
+
+<p> Example 2: censor the per-recipient delivery status text so
+that it does not reveal the destination command or filename
+when a remote sender requests confirmation of successful delivery.
+</p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#local_delivery_status_filter">local_delivery_status_filter</a> = <a href="pcre_table.5.html">pcre</a>:/etc/postfix/local_dsn_filter
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/local_dsn_filter:
+ /^(2\S+ delivered to file).+/ $1
+ /^(2\S+ delivered to command).+/ $1
+</pre>
+</blockquote>
+
+<p> Notes: </p>
+
+<ul>
+
+<li> <p> This feature will NOT override the <a href="postconf.5.html#soft_bounce">soft_bounce</a> safety net. </p>
+
+<li> <p> This feature will change the enhanced status code and text
+that is logged to the maillog file, and that is reported to the
+sender in delivery confirmation or non-delivery notifications.
+</p>
+
+</ul>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="default_destination_concurrency_failed_cohort_limit">default_destination_concurrency_failed_cohort_limit</a>
+(default: 1)</b></DT><DD>
+
+<p> How many pseudo-cohorts must suffer connection or handshake
+failure before a specific destination is considered unavailable
+(and further delivery is suspended). Specify zero to disable this
+feature. A destination's pseudo-cohort failure count is reset each
+time a delivery completes without connection or handshake failure
+for that specific destination. </p>
+
+<p> A pseudo-cohort is the number of deliveries equal to a destination's
+delivery concurrency. </p>
+
+<p> Use <a href="postconf.5.html#transport_destination_concurrency_failed_cohort_limit"><i>transport</i>_destination_concurrency_failed_cohort_limit</a> to specify
+a transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport. </p>
+
+<p> This feature is available in Postfix 2.5. The default setting
+is compatible with earlier Postfix versions. </p>
+
+
+</DD>
+
+<DT><b><a name="default_destination_concurrency_limit">default_destination_concurrency_limit</a>
+(default: 20)</b></DT><DD>
+
+<p>
+The default maximal number of parallel deliveries to the same
+destination. This is the default limit for delivery via the <a href="lmtp.8.html">lmtp(8)</a>,
+<a href="pipe.8.html">pipe(8)</a>, <a href="smtp.8.html">smtp(8)</a> and <a href="virtual.8.html">virtual(8)</a> delivery agents.
+With per-destination recipient limit &gt; 1, a destination is a domain,
+otherwise it is a recipient.
+</p>
+
+<p> Use <a href="postconf.5.html#transport_destination_concurrency_limit"><i>transport</i>_destination_concurrency_limit</a> to specify a
+transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport.
+</p>
+
+
+</DD>
+
+<DT><b><a name="default_destination_concurrency_negative_feedback">default_destination_concurrency_negative_feedback</a>
+(default: 1)</b></DT><DD>
+
+<p> The per-destination amount of delivery concurrency negative
+feedback, after a delivery completes with a connection or handshake
+failure. Feedback values are in the range 0..1 inclusive. With
+negative feedback, concurrency is decremented at the beginning of
+a sequence of length 1/feedback. This is unlike positive feedback,
+where concurrency is incremented at the end of a sequence of length
+1/feedback. </p>
+
+<p> As of Postfix version 2.5, negative feedback cannot reduce
+delivery concurrency to zero. Instead, a destination is marked
+dead (further delivery suspended) after the failed pseudo-cohort
+count reaches $<a href="postconf.5.html#default_destination_concurrency_failed_cohort_limit">default_destination_concurrency_failed_cohort_limit</a>
+(or $<a href="postconf.5.html#transport_destination_concurrency_failed_cohort_limit"><i>transport</i>_destination_concurrency_failed_cohort_limit</a>).
+To make the scheduler completely immune to connection or handshake
+failures, specify a zero feedback value and a zero failed pseudo-cohort
+limit. </p>
+
+<p> Specify one of the following forms: </p>
+
+<dl>
+
+<dt> <b><i>number</i> </b> </dt>
+
+<dt> <b><i>number</i> / <i>number</i> </b> </dt>
+
+<dd> Constant feedback. The value must be in the range 0..1 inclusive.
+The default setting of "1" is compatible with Postfix versions
+before 2.5, where a destination's delivery concurrency is throttled
+down to zero (and further delivery suspended) after a single failed
+pseudo-cohort. </dd>
+
+<dt> <b><i>number</i> / concurrency </b> </dt>
+
+<dd> Variable feedback of "<i>number</i> / (delivery concurrency)".
+The <i>number</i> must be in the range 0..1 inclusive. With
+<i>number</i> equal to "1", a destination's delivery concurrency
+is decremented by 1 after each failed pseudo-cohort. </dd>
+
+</dl>
+
+<p> A pseudo-cohort is the number of deliveries equal to a destination's
+delivery concurrency. </p>
+
+<p> Use <a href="postconf.5.html#transport_destination_concurrency_negative_feedback"><i>transport</i>_destination_concurrency_negative_feedback</a>
+to specify a transport-specific override, where <i>transport</i>
+is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport. </p>
+
+<p> This feature is available in Postfix 2.5. The default setting
+is compatible with earlier Postfix versions. </p>
+
+
+</DD>
+
+<DT><b><a name="default_destination_concurrency_positive_feedback">default_destination_concurrency_positive_feedback</a>
+(default: 1)</b></DT><DD>
+
+<p> The per-destination amount of delivery concurrency positive
+feedback, after a delivery completes without connection or handshake
+failure. Feedback values are in the range 0..1 inclusive. The
+concurrency increases until it reaches the per-destination maximal
+concurrency limit. With positive feedback, concurrency is incremented
+at the end of a sequence with length 1/feedback. This is unlike
+negative feedback, where concurrency is decremented at the start
+of a sequence of length 1/feedback. </p>
+
+<p> Specify one of the following forms: </p>
+
+<dl>
+
+<dt> <b><i>number</i> </b> </dt>
+
+<dt> <b><i>number</i> / <i>number</i> </b> </dt>
+
+<dd> Constant feedback. The value must be in the range 0..1
+inclusive. The default setting of "1" is compatible with Postfix
+versions before 2.5, where a destination's delivery concurrency
+doubles after each successful pseudo-cohort. </dd>
+
+<dt> <b><i>number</i> / concurrency </b> </dt>
+
+<dd> Variable feedback of "<i>number</i> / (delivery concurrency)".
+The <i>number</i> must be in the range 0..1 inclusive. With
+<i>number</i> equal to "1", a destination's delivery concurrency
+is incremented by 1 after each successful pseudo-cohort. </dd>
+
+</dl>
+
+<p> A pseudo-cohort is the number of deliveries equal to a destination's
+delivery concurrency. </p>
+
+<p> Use <a href="postconf.5.html#transport_destination_concurrency_positive_feedback"><i>transport</i>_destination_concurrency_positive_feedback</a>
+to specify a transport-specific override, where <i>transport</i>
+is the <a href="master.5.html">master.cf</a> name of the message delivery transport. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="default_destination_rate_delay">default_destination_rate_delay</a>
+(default: 0s)</b></DT><DD>
+
+<p> The default amount of delay that is inserted between individual
+message deliveries to the same destination and over the same message
+delivery transport. Specify a non-zero value to rate-limit those
+message deliveries to at most one per $<a href="postconf.5.html#default_destination_rate_delay">default_destination_rate_delay</a>.
+</p>
+
+<p> The resulting behavior depends on the value of the corresponding
+per-destination recipient limit.
+
+</p>
+
+<ul>
+
+<li> <p> With a corresponding per-destination recipient limit &gt;
+1, the rate delay specifies the time between deliveries to the
+<i>same domain</i>. Different domains are delivered in parallel,
+subject to the process limits specified in <a href="master.5.html">master.cf</a>. </p>
+
+<li> <p> With a corresponding per-destination recipient limit equal
+to 1, the rate delay specifies the time between deliveries to the
+<i>same recipient</i>. Different recipients are delivered in
+parallel, subject to the process limits specified in <a href="master.5.html">master.cf</a>.
+</p>
+
+</ul>
+
+<p> To enable the delay, specify a non-zero time value (an integral
+value plus an optional one-letter suffix that specifies the time
+unit). </p>
+
+<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
+(weeks). The default time unit is s (seconds). </p>
+
+<p> NOTE: the delay is enforced by the queue manager. The delay
+timer state does not survive "<b>postfix reload</b>" or "<b>postfix
+stop</b>".
+</p>
+
+<p> Use <a href="postconf.5.html#transport_destination_rate_delay"><i>transport</i>_destination_rate_delay</a> to specify a
+transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport.
+</p>
+
+<p> NOTE: with a non-zero _destination_rate_delay, specify a
+<a href="postconf.5.html#transport_destination_concurrency_failed_cohort_limit"><i>transport</i>_destination_concurrency_failed_cohort_limit</a> of 10
+or more to prevent Postfix from deferring all mail for the same
+destination after only one connection or handshake error. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="default_destination_recipient_limit">default_destination_recipient_limit</a>
+(default: 50)</b></DT><DD>
+
+<p>
+The default maximal number of recipients per message delivery.
+This is the default limit for delivery via the <a href="lmtp.8.html">lmtp(8)</a>, <a href="pipe.8.html">pipe(8)</a>,
+<a href="smtp.8.html">smtp(8)</a> and <a href="virtual.8.html">virtual(8)</a> delivery agents.
+</p>
+
+<p> Setting this parameter to a value of 1 affects email deliveries
+as follows:</p>
+
+<ul>
+
+<li> <p> It changes the meaning of the corresponding per-destination
+concurrency limit, from concurrency of deliveries to the <i>same
+domain</i> into concurrency of deliveries to the <i>same recipient</i>.
+Different recipients are delivered in parallel, subject to the
+process limits specified in <a href="master.5.html">master.cf</a>. </p>
+
+<li> <p> It changes the meaning of the corresponding per-destination
+rate delay, from the delay between deliveries to the <i>same
+domain</i> into the delay between deliveries to the <i>same
+recipient</i>. Again, different recipients are delivered in parallel,
+subject to the process limits specified in <a href="master.5.html">master.cf</a>. </p>
+
+<li> <p> It changes the meaning of other corresponding per-destination
+settings in a similar manner, from settings for delivery to the
+<i>same domain</i> into settings for delivery to the <i>same
+recipient</i>.
+
+</ul>
+
+<p> Use <a href="postconf.5.html#transport_destination_recipient_limit"><i>transport</i>_destination_recipient_limit</a> to specify a
+transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport.
+</p>
+
+
+</DD>
+
+<DT><b><a name="default_extra_recipient_limit">default_extra_recipient_limit</a>
+(default: 1000)</b></DT><DD>
+
+<p>
+The default value for the extra per-transport limit imposed on the
+number of in-memory recipients. This extra recipient space is
+reserved for the cases when the Postfix queue manager's scheduler
+preempts one message with another and suddenly needs some extra
+recipients slots for the chosen message in order to avoid performance
+degradation.
+</p>
+
+<p> Use <a href="postconf.5.html#transport_extra_recipient_limit"><i>transport</i>_extra_recipient_limit</a> to specify a
+transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport.
+</p>
+
+
+</DD>
+
+<DT><b><a name="default_filter_nexthop">default_filter_nexthop</a>
+(default: empty)</b></DT><DD>
+
+<p> When a <a href="postconf.5.html#content_filter">content_filter</a> or FILTER request specifies no explicit
+next-hop destination, use $<a href="postconf.5.html#default_filter_nexthop">default_filter_nexthop</a> instead; when
+that value is empty, use the domain in the recipient address.
+Specify "<a href="postconf.5.html#default_filter_nexthop">default_filter_nexthop</a> = $<a href="postconf.5.html#myhostname">myhostname</a>" for compatibility
+with Postfix version 2.6 and earlier, or specify an explicit next-hop
+destination with each <a href="postconf.5.html#content_filter">content_filter</a> value or FILTER action. </p>
+
+<p> This feature is available in Postfix 2.7 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="default_minimum_delivery_slots">default_minimum_delivery_slots</a>
+(default: 3)</b></DT><DD>
+
+<p>
+How many recipients a message must have in order to invoke the
+Postfix queue manager's scheduling algorithm at all. Messages
+which would never accumulate at least this many delivery slots
+(subject to slot cost parameter as well) are never preempted.
+</p>
+
+<p> Use <a href="postconf.5.html#transport_minimum_delivery_slots"><i>transport</i>_minimum_delivery_slots</a> to specify a
+transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport.
+</p>
+
+
+</DD>
+
+<DT><b><a name="default_privs">default_privs</a>
+(default: nobody)</b></DT><DD>
+
+<p>
+The default rights used by the <a href="local.8.html">local(8)</a> delivery agent for delivery
+to external file or command. These rights are used when delivery
+is requested from an <a href="aliases.5.html">aliases(5)</a> file that is owned by <b>root</b>, or
+when delivery is done on behalf of <b>root</b>. <b>DO NOT SPECIFY A
+PRIVILEGED USER OR THE POSTFIX OWNER</b>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="default_process_limit">default_process_limit</a>
+(default: 100)</b></DT><DD>
+
+<p>
+The default maximal number of Postfix child processes that provide
+a given service. This limit can be overruled for specific services
+in the <a href="master.5.html">master.cf</a> file.
+</p>
+
+
+</DD>
+
+<DT><b><a name="default_rbl_reply">default_rbl_reply</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The default Postfix SMTP server response template for a request that is
+rejected by an RBL-based restriction. This template can be overruled
+by specific entries in the optional <a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a> lookup table.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+<p>
+The template does not support Postfix configuration parameter $name
+substitution. Instead, it supports exactly one level of $name
+substitution for the following attributes:
+</p>
+
+<dl>
+
+<dt><b>$client</b></dt>
+
+<dd>The client hostname and IP address, formatted as name[address]. </dd>
+
+<dt><b>$client_address</b></dt>
+
+<dd>The client IP address. </dd>
+
+<dt><b>$client_name</b></dt>
+
+<dd>The client hostname or "unknown". See <a href="postconf.5.html#reject_unknown_client_hostname">reject_unknown_client_hostname</a>
+for more details. </dd>
+
+<dt><b>$reverse_client_name</b></dt>
+
+<dd>The client hostname from address-&gt;name lookup, or "unknown".
+See <a href="postconf.5.html#reject_unknown_reverse_client_hostname">reject_unknown_reverse_client_hostname</a> for more details. </dd>
+
+<dt><b>$helo_name</b></dt>
+
+<dd>The hostname given in HELO or EHLO command or empty string. </dd>
+
+<dt><b>$rbl_class</b></dt>
+
+<dd>The blacklisted entity type: Client host, Helo command, Sender
+address, or Recipient address. </dd>
+
+<dt><b>$rbl_code</b></dt>
+
+<dd>The numerical SMTP response code, as specified with the
+<a href="postconf.5.html#maps_rbl_reject_code">maps_rbl_reject_code</a> configuration parameter. Note: The numerical
+SMTP response code is required, and must appear at the start of the
+reply. With Postfix version 2.3 and later this information may be followed
+by an <a href="http://tools.ietf.org/html/rfc3463">RFC 3463</a> enhanced status code. </dd>
+
+<dt><b>$rbl_domain</b></dt>
+
+<dd>The RBL domain where $rbl_what is blacklisted. </dd>
+
+<dt><b>$rbl_reason</b></dt>
+
+<dd>The reason why $rbl_what is blacklisted, or an empty string. </dd>
+
+<dt><b>$rbl_what</b></dt>
+
+<dd>The entity that is blacklisted (an IP address, a hostname, a domain
+name, or an email address whose domain was blacklisted). </dd>
+
+<dt><b>$recipient</b></dt>
+
+<dd>The recipient address or &lt;&gt; in case of the null address. </dd>
+
+<dt><b>$recipient_domain</b></dt>
+
+<dd>The recipient domain or empty string. </dd>
+
+<dt><b>$recipient_name</b></dt>
+
+<dd>The recipient address localpart or &lt;&gt; in case of null address. </dd>
+
+<dt><b>$sender</b></dt>
+
+<dd>The sender address or &lt;&gt; in case of the null address. </dd>
+
+<dt><b>$sender_domain</b></dt>
+
+<dd>The sender domain or empty string. </dd>
+
+<dt><b>$sender_name</b></dt>
+
+<dd>The sender address localpart or &lt;&gt; in case of the null address. </dd>
+
+<dt><b>${name?text}</b></dt>
+
+<dd>Expands to `text' if $name is not empty. </dd>
+
+<dt><b>${name:text}</b></dt>
+
+<dd>Expands to `text' if $name is empty. </dd>
+
+</dl>
+
+<p>
+Instead of $name you can also specify ${name} or $(name).
+</p>
+
+<p> Note: when an enhanced status code is specified in an RBL reply
+template, it is subject to modification. The following transformations
+are needed when the same RBL reply template is used for client,
+helo, sender, or recipient access restrictions. </p>
+
+<ul>
+
+<li> <p> When rejecting a sender address, the Postfix SMTP server
+will transform a recipient DSN status (e.g., 4.1.1-4.1.6) into the
+corresponding sender DSN status, and vice versa. </p>
+
+<li> <p> When rejecting non-address information (such as the HELO
+command argument or the client hostname/address), the Postfix SMTP
+server will transform a sender or recipient DSN status into a generic
+non-address DSN status (e.g., 4.0.0). </p>
+
+</ul>
+
+
+</DD>
+
+<DT><b><a name="default_recipient_limit">default_recipient_limit</a>
+(default: 20000)</b></DT><DD>
+
+<p>
+The default per-transport upper limit on the number of in-memory
+recipients. These limits take priority over the global
+<a href="postconf.5.html#qmgr_message_recipient_limit">qmgr_message_recipient_limit</a> after the message has been assigned
+to the respective transports. See also <a href="postconf.5.html#default_extra_recipient_limit">default_extra_recipient_limit</a>
+and <a href="postconf.5.html#qmgr_message_recipient_minimum">qmgr_message_recipient_minimum</a>.
+</p>
+
+<p> Use <a href="postconf.5.html#transport_recipient_limit"><i>transport</i>_recipient_limit</a> to specify a
+transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport.
+</p>
+
+
+</DD>
+
+<DT><b><a name="default_recipient_refill_delay">default_recipient_refill_delay</a>
+(default: 5s)</b></DT><DD>
+
+<p>
+The default per-transport maximum delay between recipients refills.
+When not all message recipients fit into the memory at once, keep loading
+more of them at least once every this many seconds. This is used to
+make sure the recipients are refilled in timely manner even when
+$<a href="postconf.5.html#default_recipient_refill_limit">default_recipient_refill_limit</a> is too high for too slow deliveries.
+</p>
+
+<p> Use <a href="postconf.5.html#transport_recipient_refill_delay"><i>transport</i>_recipient_refill_delay</a> to specify a
+transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport.
+</p>
+
+<p> This feature is available in Postfix 2.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="default_recipient_refill_limit">default_recipient_refill_limit</a>
+(default: 100)</b></DT><DD>
+
+<p>
+The default per-transport limit on the number of recipients refilled at
+once. When not all message recipients fit into the memory at once, keep
+loading more of them in batches of at least this many at a time. See also
+$<a href="postconf.5.html#default_recipient_refill_delay">default_recipient_refill_delay</a>, which may result in recipient batches
+lower than this when this limit is too high for too slow deliveries.
+</p>
+
+<p> Use <a href="postconf.5.html#transport_recipient_refill_limit"><i>transport</i>_recipient_refill_limit</a> to specify a
+transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport.
+</p>
+
+<p> This feature is available in Postfix 2.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="default_transport">default_transport</a>
+(default: smtp)</b></DT><DD>
+
+<p>
+The default mail delivery transport and next-hop destination for
+destinations that do not match $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>,
+$<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>, $<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>,
+or $<a href="postconf.5.html#relay_domains">relay_domains</a>. This information can be overruled with the
+<a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a> parameter and with the
+<a href="transport.5.html">transport(5)</a> table. </p>
+
+<p>
+In order of decreasing precedence, the nexthop destination is taken
+from $<a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a>, $<a href="postconf.5.html#default_transport">default_transport</a>,
+$<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>, $<a href="postconf.5.html#relayhost">relayhost</a>, or from the recipient
+domain.
+</p>
+
+<p>
+Specify a string of the form <i>transport:nexthop</i>, where <i>transport</i>
+is the name of a mail delivery transport defined in <a href="master.5.html">master.cf</a>.
+The <i>:nexthop</i> destination is optional; its syntax is documented
+in the manual page of the corresponding delivery agent.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#default_transport">default_transport</a> = uucp:relayhostname
+</pre>
+
+
+</DD>
+
+<DT><b><a name="default_transport_rate_delay">default_transport_rate_delay</a>
+(default: 0s)</b></DT><DD>
+
+<p> The default amount of delay that is inserted between individual
+message deliveries over the same message delivery transport,
+regardless of destination. Specify a non-zero value to rate-limit
+those message deliveries to at most one per $<a href="postconf.5.html#default_transport_rate_delay">default_transport_rate_delay</a>.
+</p>
+
+<p>Use <a href="postconf.5.html#transport_transport_rate_delay"><i>transport</i>_transport_rate_delay</a> to specify a
+transport-specific override, where the initial <i>transport</i> is
+the <a href="master.5.html">master.cf</a> name of the message delivery transport. </p>
+
+<p> Example: throttle outbound SMTP mail to at most 3 deliveries
+per minute. </p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ smtp_transport_rate_delay = 20s
+</pre>
+
+<p> To enable the delay, specify a non-zero time value (an integral
+value plus an optional one-letter suffix that specifies the time
+unit). </p>
+
+<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
+(weeks). The default time unit is s (seconds). </p>
+
+<p> NOTE: the delay is enforced by the queue manager. </p>
+
+<p> This feature is available in Postfix 3.1 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="default_verp_delimiters">default_verp_delimiters</a>
+(default: +=)</b></DT><DD>
+
+<p> The two default VERP delimiter characters. These are used when
+no explicit delimiters are specified with the SMTP XVERP command
+or with the "<b>sendmail -V</b>" command-line option. Specify
+characters that are allowed by the <a href="postconf.5.html#verp_delimiter_filter">verp_delimiter_filter</a> setting.
+</p>
+
+<p>
+This feature is available in Postfix 1.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="defer_code">defer_code</a>
+(default: 450)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code when a remote SMTP
+client request is rejected by the "defer" restriction.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="defer_service_name">defer_service_name</a>
+(default: defer)</b></DT><DD>
+
+<p>
+The name of the defer service. This service is implemented by the
+<a href="bounce.8.html">bounce(8)</a> daemon and maintains a record
+of failed delivery attempts and generates non-delivery notifications.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="defer_transports">defer_transports</a>
+(default: empty)</b></DT><DD>
+
+<p>
+The names of message delivery transports that should not deliver mail
+unless someone issues "<b>sendmail -q</b>" or equivalent. Specify zero
+or more names of mail delivery transports names that appear in the
+first field of <a href="master.5.html">master.cf</a>.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#defer_transports">defer_transports</a> = smtp
+</pre>
+
+
+</DD>
+
+<DT><b><a name="delay_logging_resolution_limit">delay_logging_resolution_limit</a>
+(default: 2)</b></DT><DD>
+
+<p> The maximal number of digits after the decimal point when logging
+sub-second delay values. Specify a number in the range 0..6. </p>
+
+<p> Large delay values are rounded off to an integral number seconds;
+delay values below the <a href="postconf.5.html#delay_logging_resolution_limit">delay_logging_resolution_limit</a> are logged
+as "0", and delay values under 100s are logged with at most two-digit
+precision. </p>
+
+<p> The format of the "delays=a/b/c/d" logging is as follows: </p>
+
+<ul>
+
+<li> a = time from message arrival to last <a href="QSHAPE_README.html#active_queue">active queue</a> entry
+
+<li> b = time from last <a href="QSHAPE_README.html#active_queue">active queue</a> entry to connection setup
+
+<li> c = time in connection setup, including DNS, EHLO and STARTTLS
+
+<li> d = time in message transmission
+
+</ul>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="delay_notice_recipient">delay_notice_recipient</a>
+(default: postmaster)</b></DT><DD>
+
+<p>
+The recipient of postmaster notifications with the message headers
+of mail that cannot be delivered within $<a href="postconf.5.html#delay_warning_time">delay_warning_time</a> time
+units. </p>
+
+<p>
+See also: <a href="postconf.5.html#delay_warning_time">delay_warning_time</a>, <a href="postconf.5.html#notify_classes">notify_classes</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="delay_warning_time">delay_warning_time</a>
+(default: 0h)</b></DT><DD>
+
+<p>
+The time after which the sender receives a copy of the message
+headers of mail that is still queued. The <a href="postconf.5.html#confirm_delay_cleared">confirm_delay_cleared</a>
+parameter controls sender notification when the delay clears up.
+</p>
+
+<p>
+To enable this feature, specify a non-zero time value (an integral
+value plus an optional one-letter suffix that specifies the time
+unit).
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is h (hours).
+</p>
+
+<p>
+See also: <a href="postconf.5.html#delay_notice_recipient">delay_notice_recipient</a>, <a href="postconf.5.html#notify_classes">notify_classes</a>, <a href="postconf.5.html#confirm_delay_cleared">confirm_delay_cleared</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="deliver_lock_attempts">deliver_lock_attempts</a>
+(default: 20)</b></DT><DD>
+
+<p>
+The maximal number of attempts to acquire an exclusive lock on a
+mailbox file or <a href="bounce.8.html">bounce(8)</a> logfile.
+</p>
+
+
+</DD>
+
+<DT><b><a name="deliver_lock_delay">deliver_lock_delay</a>
+(default: 1s)</b></DT><DD>
+
+<p>
+The time between attempts to acquire an exclusive lock on a mailbox
+file or <a href="bounce.8.html">bounce(8)</a> logfile.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="destination_concurrency_feedback_debug">destination_concurrency_feedback_debug</a>
+(default: no)</b></DT><DD>
+
+<p> Make the queue manager's feedback algorithm verbose for performance
+analysis purposes. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="detect_8bit_encoding_header">detect_8bit_encoding_header</a>
+(default: yes)</b></DT><DD>
+
+<p> Automatically detect 8BITMIME body content by looking at
+Content-Transfer-Encoding: message headers; historically, this
+behavior was hard-coded to be "always on". </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="disable_dns_lookups">disable_dns_lookups</a>
+(default: no)</b></DT><DD>
+
+<p>
+Disable DNS lookups in the Postfix SMTP and LMTP clients. When
+disabled, hosts are looked up with the getaddrinfo() system
+library routine which normally also looks in /etc/hosts. As of
+Postfix 2.11, this parameter is deprecated; use <a href="postconf.5.html#smtp_dns_support_level">smtp_dns_support_level</a>
+instead.
+</p>
+
+<p>
+DNS lookups are enabled by default.
+</p>
+
+
+</DD>
+
+<DT><b><a name="disable_mime_input_processing">disable_mime_input_processing</a>
+(default: no)</b></DT><DD>
+
+<p>
+Turn off MIME processing while receiving mail. This means that no
+special treatment is given to Content-Type: message headers, and
+that all text after the initial message headers is considered to
+be part of the message body.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+<p>
+Mime input processing is enabled by default, and is needed in order
+to recognize MIME headers in message content.
+</p>
+
+
+</DD>
+
+<DT><b><a name="disable_mime_output_conversion">disable_mime_output_conversion</a>
+(default: no)</b></DT><DD>
+
+<p>
+Disable the conversion of 8BITMIME format to 7BIT format. Mime
+output conversion is needed when the destination does not advertise
+8BITMIME support.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="disable_verp_bounces">disable_verp_bounces</a>
+(default: no)</b></DT><DD>
+
+<p>
+Disable sending one bounce report per recipient.
+</p>
+
+<p>
+The default, one per recipient, is what ezmlm needs.
+</p>
+
+<p>
+This feature is available in Postfix 1.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="disable_vrfy_command">disable_vrfy_command</a>
+(default: no)</b></DT><DD>
+
+<p>
+Disable the SMTP VRFY command. This stops some techniques used to
+harvest email addresses.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#disable_vrfy_command">disable_vrfy_command</a> = no
+</pre>
+
+
+</DD>
+
+<DT><b><a name="dns_ncache_ttl_fix_enable">dns_ncache_ttl_fix_enable</a>
+(default: no)</b></DT><DD>
+
+<p> Enable a workaround for future libc incompatibility. The Postfix
+implementation of <a href="http://tools.ietf.org/html/rfc2308">RFC 2308</a> negative reply caching relies on the
+promise that res_query() and res_search() invoke res_send(), which
+returns the server response in an application buffer even if the
+requested record does not exist. If this promise is broken, specify
+"yes" to enable a workaround for DNS reputation lookups. </p>
+
+<p>
+This feature is available in Postfix 3.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="dnsblog_reply_delay">dnsblog_reply_delay</a>
+(default: 0s)</b></DT><DD>
+
+<p> A debugging aid to artificially delay DNS responses. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="dnsblog_service_name">dnsblog_service_name</a>
+(default: dnsblog)</b></DT><DD>
+
+<p> The name of the <a href="dnsblog.8.html">dnsblog(8)</a> service entry in <a href="master.5.html">master.cf</a>. This
+service performs DNS white/blacklist lookups. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="dnssec_probe">dnssec_probe</a>
+(default: ns:.)</b></DT><DD>
+
+<p> The DNS query type (default: "ns") and DNS query name (default:
+".") that Postfix may use to determine whether DNSSEC validation
+is available.
+</p>
+
+<p> Background: DNSSEC validation is needed for Postfix DANE support;
+this ensures that Postfix receives TLSA records with secure TLS
+server certificate info. When DNSSEC validation is unavailable,
+mail deliveries using <i>opportunistic</i> DANE will not be protected
+by server certificate info in TLSA records, and mail deliveries
+using <i>mandatory</i> DANE will not be made at all. </p>
+
+<p> By default, a Postfix process will send a DNSSEC probe after
+1) the process made a DNS query that requested DNSSEC validation,
+2) the process did not receive a DNSSEC validated response to this
+query or to an earlier query, and 3) the process did not already
+send a DNSSEC probe. <p>
+
+<p> When the DNSSEC probe has no response, or when the response is
+not DNSSEC validated, Postfix logs a warning that DNSSEC validation
+may be unavailable. </p>
+
+<p> Example: </p>
+
+<pre>
+warning: DNSSEC validation may be unavailable
+warning: reason: <a href="postconf.5.html#dnssec_probe">dnssec_probe</a> 'ns:.' received a response that is not DNSSEC validated
+warning: reason: <a href="postconf.5.html#dnssec_probe">dnssec_probe</a> 'ns:.' received no response: Server failure
+</pre>
+
+<p> Possible reasons why DNSSEC validation may be unavailable: </p>
+
+<ul>
+
+<li> The local /etc/resolv.conf file specifies a DNS resolver that
+does not validate DNSSEC signatures (that's
+$<a href="postconf.5.html#queue_directory">queue_directory</a>/etc/resolv.conf when a Postfix daemon runs in a
+chroot jail).
+
+<li> The local system library does not pass on the "DNSSEC validated"
+bit to Postfix, or Postfix does not know how to ask the library to
+do that.
+
+</ul>
+
+<p> By default, the DNSSEC probe asks for the DNS root zone NS
+records, because resolvers should always have that information
+cached. If Postfix runs on a network where the DNS root zone is not
+reachable, specify a different probe, or specify an empty <a href="postconf.5.html#dnssec_probe">dnssec_probe</a>
+value to disable the feature. </p>
+
+<p> This feature was backported from Postfix 3.6 to Postfix versions
+3.5.9, 3.4.19, 3.3.16. 3.2.21. </p>
+
+
+</DD>
+
+<DT><b><a name="dont_remove">dont_remove</a>
+(default: 0)</b></DT><DD>
+
+<p>
+Don't remove queue files and save them to the "saved" mail queue.
+This is a debugging aid. To inspect the envelope information and
+content of a Postfix queue file, use the <a href="postcat.1.html">postcat(1)</a> command.
+</p>
+
+
+</DD>
+
+<DT><b><a name="double_bounce_sender">double_bounce_sender</a>
+(default: double-bounce)</b></DT><DD>
+
+<p> The sender address of postmaster notifications that are generated
+by the mail system. All mail to this address is silently discarded,
+in order to terminate mail bounce loops. </p>
+
+
+</DD>
+
+<DT><b><a name="duplicate_filter_limit">duplicate_filter_limit</a>
+(default: 1000)</b></DT><DD>
+
+<p> The maximal number of addresses remembered by the address
+duplicate filter for <a href="aliases.5.html">aliases(5)</a> or <a href="virtual.5.html">virtual(5)</a> alias expansion, or
+for <a href="showq.8.html">showq(8)</a> queue displays. </p>
+
+
+</DD>
+
+<DT><b><a name="empty_address_default_transport_maps_lookup_key">empty_address_default_transport_maps_lookup_key</a>
+(default: &lt;&gt;)</b></DT><DD>
+
+<p> The <a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a> search string that
+will be used instead of the null sender address. </p>
+
+<p> This feature is available in Postfix 2.7 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="empty_address_recipient">empty_address_recipient</a>
+(default: MAILER-DAEMON)</b></DT><DD>
+
+<p>
+The recipient of mail addressed to the null address. Postfix does
+not accept such addresses in SMTP commands, but they may still be
+created locally as the result of configuration or software error.
+</p>
+
+
+</DD>
+
+<DT><b><a name="empty_address_relayhost_maps_lookup_key">empty_address_relayhost_maps_lookup_key</a>
+(default: &lt;&gt;)</b></DT><DD>
+
+<p> The <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> search string that will be
+used instead of the null sender address. </p>
+
+<p> This feature is available in Postfix 2.5 and later. With
+earlier versions, <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> lookups were
+skipped for the null sender address. </p>
+
+
+</DD>
+
+<DT><b><a name="enable_errors_to">enable_errors_to</a>
+(default: no)</b></DT><DD>
+
+<p> Report mail delivery errors to the address specified with the
+non-standard Errors-To: message header, instead of the envelope
+sender address (this feature is removed with Postfix version 2.2, is
+turned off by default with Postfix version 2.1, and is always turned on
+with older Postfix versions). </p>
+
+
+</DD>
+
+<DT><b><a name="enable_idna2003_compatibility">enable_idna2003_compatibility</a>
+(default: no)</b></DT><DD>
+
+<p> Enable 'transitional' compatibility between IDNA2003 and IDNA2008,
+when converting UTF-8 domain names to/from the ASCII form that is
+used for DNS lookups. Specify "yes" for compatibility with Postfix
+&le; 3.1 (not recommended). This affects the conversion of domain
+names that contain for example the German sz and the Greek zeta.
+See <a href="http://unicode.org/cldr/utility/idna.jsp">http://unicode.org/cldr/utility/idna.jsp</a> for more examples.
+</p>
+
+<p> This feature is available in Postfix 3.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="enable_long_queue_ids">enable_long_queue_ids</a>
+(default: no)</b></DT><DD>
+
+<p> Enable long, non-repeating, queue IDs (queue file names). The
+benefit of non-repeating names is simpler logfile analysis and
+easier queue migration (there is no need to run "postsuper" to
+change queue file names that don't match their message file inode
+number). </p>
+
+<p> Note: see below for how to convert long queue file names to
+Postfix &le; 2.8. </p>
+
+<p> Changing the parameter value to "yes" has the following effects:
+</p>
+
+<ul>
+
+<li> <p> Existing queue file names are not affected. </p>
+
+<li> <p> New queue files are created with names such as 3Pt2mN2VXxznjll.
+These are encoded in a 52-character alphabet that contains digits
+(0-9), upper-case letters (B-Z) and lower-case letters (b-z). For
+safety reasons the vowels (AEIOUaeiou) are excluded from the alphabet.
+The name format is: 6 or more characters for the time in seconds,
+4 characters for the time in microseconds, the 'z'; the remainder
+is the file inode number encoded in the first 51 characters of the
+52-character alphabet. </p>
+
+<li> <p> New messages have a Message-ID header with
+<i>queueID</i>@<i><a href="postconf.5.html#myhostname">myhostname</a></i>. </p>
+
+<li> <p> The mailq (postqueue -p) output has a wider Queue ID column.
+The number of whitespace-separated fields is not changed. <p>
+
+<li> <p> The <a href="postconf.5.html#hash_queue_depth">hash_queue_depth</a> algorithm uses the first characters
+of the queue file creation time in microseconds, after conversion
+into hexadecimal representation. This produces the same queue hashing
+behavior as if the queue file name was created with "<a href="postconf.5.html#enable_long_queue_ids">enable_long_queue_ids</a>
+= no". </p>
+
+</ul>
+
+<p> Changing the parameter value to "no" has the following effects:
+</p>
+
+<ul>
+
+<li> <p> Existing long queue file names are renamed to the short
+form (while running "postfix reload" or "postsuper"). </p>
+
+<li> <p> New queue files are created with names such as C3CD21F3E90
+from a hexadecimal alphabet that contains digits (0-9) and upper-case
+letters (A-F). The name format is: 5 characters for the time in
+microseconds; the remainder is the file inode number. </p>
+
+<li> <p> New messages have a Message-ID header with
+<i>YYYYMMDDHHMMSS.queueid</i>@<i><a href="postconf.5.html#myhostname">myhostname</a></i>, where
+<i>YYYYMMDDHHMMSS</i> are the year, month, day, hour, minute and
+second.
+
+<li> <p> The mailq (postqueue -p) output has the same format as
+with Postfix &le; 2.8. <p>
+
+<li> <p> The <a href="postconf.5.html#hash_queue_depth">hash_queue_depth</a> algorithm uses the first characters
+of the queue file name, with the hexadecimal representation of the
+file creation time in microseconds. </p>
+
+</ul>
+
+<p> Before migration to Postfix &le; 2.8, the following commands
+are required to convert long queue file names into short names: </p>
+
+<pre>
+# postfix stop
+# postconf <a href="postconf.5.html#enable_long_queue_ids">enable_long_queue_ids</a>=no
+# postsuper
+</pre>
+
+<p> Repeat the postsuper command until it reports no more queue file
+name changes. </p>
+
+<p> This feature is available in Postfix 2.9 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="enable_original_recipient">enable_original_recipient</a>
+(default: yes)</b></DT><DD>
+
+<p> Enable support for the original recipient address after an
+address is rewritten to a different address (for example with
+aliasing or with canonical mapping). </p>
+
+<p> The original recipient address is used as follows: </p>
+
+<dl>
+
+<dt> Final delivery </dt> <dd> With "<a href="postconf.5.html#enable_original_recipient">enable_original_recipient</a> =
+yes", the original recipient address is stored in the <b>X-Original-To</b>
+message header. This header may be used to distinguish between
+different recipients that share the same mailbox. </dd>
+
+<dt> Recipient deduplication </dt> <dd> With "<a href="postconf.5.html#enable_original_recipient">enable_original_recipient</a>
+= yes", the <a href="cleanup.8.html">cleanup(8)</a> daemon performs duplicate recipient elimination
+based on the content of (original recipient, maybe-rewritten
+recipient) pairs. Otherwise, the <a href="cleanup.8.html">cleanup(8)</a> daemon performs duplicate
+recipient elimination based only on the maybe-rewritten recipient
+address. </dd>
+
+</dl>
+
+<p> Note: with Postfix &le; 3.2 the "setting <a href="postconf.5.html#enable_original_recipient">enable_original_recipient</a>
+= <b>no</b>" breaks address verification for addresses that are
+aliased or otherwise rewritten (Postfix is unable to store the
+address verification result under the original probe destination
+address; instead, it can store the result only under the rewritten
+address). </p>
+
+<p> This feature is available in Postfix 2.1 and later. Postfix
+version 2.0 behaves as if this parameter is always set to <b>yes</b>.
+Postfix versions before 2.0 have no support for the original recipient
+address. </p>
+
+
+</DD>
+
+<DT><b><a name="error_notice_recipient">error_notice_recipient</a>
+(default: postmaster)</b></DT><DD>
+
+<p> The recipient of postmaster notifications about mail delivery
+problems that are caused by policy, resource, software or protocol
+errors. These notifications are enabled with the <a href="postconf.5.html#notify_classes">notify_classes</a>
+parameter. </p>
+
+
+</DD>
+
+<DT><b><a name="error_service_name">error_service_name</a>
+(default: error)</b></DT><DD>
+
+<p>
+The name of the <a href="error.8.html">error(8)</a> pseudo delivery agent. This service always
+returns mail as undeliverable.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="execution_directory_expansion_filter">execution_directory_expansion_filter</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> Restrict the characters that the <a href="local.8.html">local(8)</a> delivery agent allows
+in $name expansions of $<a href="postconf.5.html#command_execution_directory">command_execution_directory</a>. Characters
+outside the allowed set are replaced by underscores. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="expand_owner_alias">expand_owner_alias</a>
+(default: no)</b></DT><DD>
+
+<p>
+When delivering to an alias "<i>aliasname</i>" that has an
+"owner-<i>aliasname</i>" companion alias, set the envelope sender
+address to the expansion of the "owner-<i>aliasname</i>" alias.
+Normally, Postfix sets the envelope sender address to the name of
+the "owner-<i>aliasname</i>" alias.
+</p>
+
+
+</DD>
+
+<DT><b><a name="export_environment">export_environment</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The list of environment variables that a Postfix process will export
+to non-Postfix processes. The TZ variable is needed for sane
+time keeping on System-V-ish systems.
+</p>
+
+<p>
+Specify a list of names and/or name=value pairs, separated by
+whitespace or comma. Specify "{ name=value }" to protect whitespace
+or comma in parameter values (whitespace after the opening "{" and
+before the closing "}"
+is ignored). The form name=value is supported with Postfix version
+2.1 and later; the use of {} is supported with Postfix 3.0 and
+later. </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#export_environment">export_environment</a> = TZ PATH=/bin:/usr/bin
+</pre>
+
+
+</DD>
+
+<DT><b><a name="extract_recipient_limit">extract_recipient_limit</a>
+(default: 10240)</b></DT><DD>
+
+<p>
+The maximal number of recipient addresses that Postfix will extract
+from message headers when mail is submitted with "<b>sendmail -t</b>".
+</p>
+
+<p>
+This feature was removed in Postfix version 2.1.
+</p>
+
+
+</DD>
+
+<DT><b><a name="fallback_relay">fallback_relay</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional list of relay hosts for SMTP destinations that can't be
+found or that are unreachable. With Postfix 2.3 this parameter
+is renamed to <a href="postconf.5.html#smtp_fallback_relay">smtp_fallback_relay</a>. </p>
+
+<p>
+By default, mail is returned to the sender when a destination is
+not found, and delivery is deferred when a destination is unreachable.
+</p>
+
+<p> The fallback relays must be SMTP destinations. Specify a domain,
+host, host:port, [host]:port, [address] or [address]:port; the form
+[host] turns off MX lookups. If you specify multiple SMTP
+destinations, Postfix will try them in the specified order. </p>
+
+<p> Note: before Postfix 2.2, do not use the <a href="postconf.5.html#fallback_relay">fallback_relay</a> feature
+when relaying mail
+for a backup or primary MX domain. Mail would loop between the
+Postfix MX host and the <a href="postconf.5.html#fallback_relay">fallback_relay</a> host when the final destination
+is unavailable. </p>
+
+<ul>
+
+<li> In <a href="postconf.5.html">main.cf</a> specify "<a href="postconf.5.html#relay_transport">relay_transport</a> = relay",
+
+<li> In <a href="master.5.html">master.cf</a> specify "-o <a href="postconf.5.html#fallback_relay">fallback_relay</a> =" (i.e., empty) at
+the end of the <tt>relay</tt> entry.
+
+<li> In transport maps, specify "relay:<i>nexthop...</i>"
+as the right-hand side for backup or primary MX domain entries.
+
+</ul>
+
+<p> Postfix version 2.2 and later will not use the <a href="postconf.5.html#fallback_relay">fallback_relay</a> feature
+for destinations that it is MX host for.
+</p>
+
+
+</DD>
+
+<DT><b><a name="fallback_transport">fallback_transport</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional message delivery transport that the <a href="local.8.html">local(8)</a> delivery
+agent should use for names that are not found in the <a href="aliases.5.html">aliases(5)</a>
+or UNIX password database.
+</p>
+
+<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
+is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
+<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
+<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. </p>
+
+
+</DD>
+
+<DT><b><a name="fallback_transport_maps">fallback_transport_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional lookup tables with per-recipient message delivery
+transports for recipients that the <a href="local.8.html">local(8)</a> delivery agent could
+not find in the <a href="aliases.5.html">aliases(5)</a> or UNIX password database. </p>
+
+<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
+is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
+<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
+<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. </p>
+
+<p> For safety reasons, this feature does not allow $number
+substitutions in regular expression maps. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="fast_flush_domains">fast_flush_domains</a>
+(default: $<a href="postconf.5.html#relay_domains">relay_domains</a>)</b></DT><DD>
+
+<p>
+Optional list of destinations that are eligible for per-destination
+logfiles with mail that is queued to those destinations.
+</p>
+
+<p>
+By default, Postfix maintains "fast flush" logfiles only for
+destinations that the Postfix SMTP server is willing to relay to
+(i.e. the default is: "<a href="postconf.5.html#fast_flush_domains">fast_flush_domains</a> = $<a href="postconf.5.html#relay_domains">relay_domains</a>"; see
+the <a href="postconf.5.html#relay_domains">relay_domains</a> parameter in the <a href="postconf.5.html">postconf(5)</a> manual).
+</p>
+
+<p> Specify a list of hosts or domains, "/file/name" patterns or
+"<a href="DATABASE_README.html">type:table</a>" lookup tables, separated by commas and/or whitespace.
+Continue long lines by starting the next line with whitespace. A
+"/file/name" pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>"
+lookup table is matched when the domain or its parent domain appears
+as lookup key. </p>
+
+<p> Pattern matching of domain names is controlled by the presence
+or absence of "<a href="postconf.5.html#fast_flush_domains">fast_flush_domains</a>" in the <a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a>
+parameter value. </p>
+
+<p>
+Specify "<a href="postconf.5.html#fast_flush_domains">fast_flush_domains</a> =" (i.e., empty) to disable the feature
+altogether.
+</p>
+
+
+</DD>
+
+<DT><b><a name="fast_flush_purge_time">fast_flush_purge_time</a>
+(default: 7d)</b></DT><DD>
+
+<p>
+The time after which an empty per-destination "fast flush" logfile
+is deleted.
+</p>
+
+<p>
+You can specify the time as a number, or as a number followed by
+a letter that indicates the time unit: s=seconds, m=minutes, h=hours,
+d=days, w=weeks. The default time unit is days.
+</p>
+
+
+</DD>
+
+<DT><b><a name="fast_flush_refresh_time">fast_flush_refresh_time</a>
+(default: 12h)</b></DT><DD>
+
+<p>
+The time after which a non-empty but unread per-destination "fast
+flush" logfile needs to be refreshed. The contents of a logfile
+are refreshed by requesting delivery of all messages listed in the
+logfile.
+</p>
+
+<p>
+You can specify the time as a number, or as a number followed by
+a letter that indicates the time unit: s=seconds, m=minutes, h=hours,
+d=days, w=weeks. The default time unit is hours.
+</p>
+
+
+</DD>
+
+<DT><b><a name="fault_injection_code">fault_injection_code</a>
+(default: 0)</b></DT><DD>
+
+<p>
+Force specific internal tests to fail, to test the handling of
+errors that are difficult to reproduce otherwise.
+</p>
+
+
+</DD>
+
+<DT><b><a name="flush_service_name">flush_service_name</a>
+(default: flush)</b></DT><DD>
+
+<p>
+The name of the <a href="flush.8.html">flush(8)</a> service. This service maintains per-destination
+logfiles with the queue file names of mail that is queued for those
+destinations.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="fork_attempts">fork_attempts</a>
+(default: 5)</b></DT><DD>
+
+<p> The maximal number of attempts to fork() a child process. </p>
+
+
+</DD>
+
+<DT><b><a name="fork_delay">fork_delay</a>
+(default: 1s)</b></DT><DD>
+
+<p> The delay between attempts to fork() a child process. </p>
+
+<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
+(weeks). The default time unit is s (seconds). </p>
+
+
+</DD>
+
+<DT><b><a name="forward_expansion_filter">forward_expansion_filter</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+Restrict the characters that the <a href="local.8.html">local(8)</a> delivery agent allows in
+$name expansions of $<a href="postconf.5.html#forward_path">forward_path</a>. Characters outside the
+allowed set are replaced by underscores.
+</p>
+
+
+</DD>
+
+<DT><b><a name="forward_path">forward_path</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The <a href="local.8.html">local(8)</a> delivery agent search list for finding a .forward
+file with user-specified delivery methods. The first file that is
+found is used. </p>
+
+<p> The <a href="postconf.5.html#forward_path">forward_path</a> value is not subject to Postfix configuration
+parameter $name expansion. Instead, the following $name expansions
+are done on <a href="postconf.5.html#forward_path">forward_path</a> before the search actually happens.
+The result of $name expansion is
+filtered with the character set that is specified with the
+<a href="postconf.5.html#forward_expansion_filter">forward_expansion_filter</a> parameter. </p>
+
+<dl>
+
+<dt><b>$user</b></dt>
+
+<dd>The recipient's username. </dd>
+
+<dt><b>$shell</b></dt>
+
+<dd>The recipient's login shell pathname. </dd>
+
+<dt><b>$home</b></dt>
+
+<dd>The recipient's home directory. </dd>
+
+<dt><b>$recipient</b></dt>
+
+<dd>The full recipient address. </dd>
+
+<dt><b>$extension</b></dt>
+
+<dd>The optional recipient address extension. </dd>
+
+<dt><b>$domain</b></dt>
+
+<dd>The recipient domain. </dd>
+
+<dt><b>$local</b></dt>
+
+<dd>The entire recipient localpart. </dd>
+
+<dt><b>$<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a></b></dt>
+
+<dd>The address extension delimiter that was found in the recipient
+address (Postfix 2.11 and later), or the system-wide recipient
+address extension delimiter (Postfix 2.10 and earlier). </dd>
+
+<dt><b>${name?value}</b></dt>
+
+<dd>Expands to <i>value</i> when <i>$name</i> is non-empty. </dd>
+
+<dt><b>${name:value}</b></dt>
+
+<dd>Expands to <i>value</i> when <i>$name</i> is empty. </dd>
+
+</dl>
+
+<p>
+Instead of $name you can also specify ${name} or $(name).
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#forward_path">forward_path</a> = /var/forward/$user
+<a href="postconf.5.html#forward_path">forward_path</a> =
+ /var/forward/$user/.forward$<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>$extension,
+ /var/forward/$user/.forward
+</pre>
+
+
+</DD>
+
+<DT><b><a name="frozen_delivered_to">frozen_delivered_to</a>
+(default: yes)</b></DT><DD>
+
+<p> Update the <a href="local.8.html">local(8)</a> delivery agent's idea of the Delivered-To:
+address (see <a href="postconf.5.html#prepend_delivered_header">prepend_delivered_header</a>) only once, at the start of
+a delivery attempt; do not update the Delivered-To: address while
+expanding aliases or .forward files. </p>
+
+<p> This feature is available in Postfix 2.3 and later. With older
+Postfix releases, the behavior is as if this parameter is set to
+"no". The old setting can be expensive with deeply nested aliases
+or .forward files. When an alias or .forward file changes the
+Delivered-To: address, it ties up one queue file and one cleanup
+process instance while mail is being forwarded. </p>
+
+
+</DD>
+
+<DT><b><a name="hash_queue_depth">hash_queue_depth</a>
+(default: 1)</b></DT><DD>
+
+<p>
+The number of subdirectory levels for queue directories listed with
+the <a href="postconf.5.html#hash_queue_names">hash_queue_names</a> parameter. Queue hashing is implemented by
+creating one or more levels of directories with one-character names.
+Originally, these directory names were equal to the first characters
+of the queue file name, with the hexadecimal representation of the
+file creation time in microseconds. </p>
+
+<p> With long queue file names, queue hashing produces the same
+results as with short names. The file creation time in microseconds
+is converted into hexadecimal form before the result is used for
+queue hashing. The base 16 encoding gives finer control over the
+number of subdirectories than is possible with the base 52 encoding
+of long queue file names. </p>
+
+<p>
+After changing the <a href="postconf.5.html#hash_queue_names">hash_queue_names</a> or <a href="postconf.5.html#hash_queue_depth">hash_queue_depth</a> parameter,
+execute the command "<b>postfix reload</b>".
+</p>
+
+
+</DD>
+
+<DT><b><a name="hash_queue_names">hash_queue_names</a>
+(default: deferred, defer)</b></DT><DD>
+
+<p>
+The names of queue directories that are split across multiple
+subdirectory levels.
+</p>
+
+<p> Before Postfix version 2.2, the default list of hashed queues
+was significantly larger. Claims about improvements in file system
+technology suggest that hashing of the <a href="QSHAPE_README.html#incoming_queue">incoming</a> and <a href="QSHAPE_README.html#active_queue">active queues</a>
+is no longer needed. Fewer hashed directories speed up the time
+needed to restart Postfix. </p>
+
+<p>
+After changing the <a href="postconf.5.html#hash_queue_names">hash_queue_names</a> or <a href="postconf.5.html#hash_queue_depth">hash_queue_depth</a> parameter,
+execute the command "<b>postfix reload</b>".
+</p>
+
+
+</DD>
+
+<DT><b><a name="header_address_token_limit">header_address_token_limit</a>
+(default: 10240)</b></DT><DD>
+
+<p>
+The maximal number of address tokens are allowed in an address
+message header. Information that exceeds the limit is discarded.
+The limit is enforced by the <a href="cleanup.8.html">cleanup(8)</a> server.
+</p>
+
+
+</DD>
+
+<DT><b><a name="header_checks">header_checks</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional lookup tables for content inspection of primary non-MIME
+message headers, as specified in the <a href="header_checks.5.html">header_checks(5)</a> manual page.
+</p>
+
+
+</DD>
+
+<DT><b><a name="header_from_format">header_from_format</a>
+(default: standard)</b></DT><DD>
+
+<p> The format of the Postfix-generated <b>From:</b> header. This
+setting affects the appearance of 'full name' information when a
+local program such as /bin/mail submits a message without From:
+header through the Postfix <a href="sendmail.1.html">sendmail(1)</a> command. </p>
+
+<p> Specify one of the following: </p>
+
+<dl>
+
+<dt><b>standard</b> (default)</dt> <dd> Produce a header formatted
+as "<b>From:</b> <i>name</i><b> &lt;</b><i>address</i><b>&gt;</b>".
+This is the default as of Postfix 3.3.</dd>
+
+<dt><b>obsolete</b></dt> <dd>Produce a header formatted as "<b>From:</b>
+<i>address</i> <b>(</b><i>name</i><b>)</b>". This is the behavior
+prior to Postfix 3.3. </dd>
+
+</dl>
+
+<p> Notes: </p>
+
+<ul>
+
+<li> <p> Postfix generates the format "<b>From:</b> <i>address</i>"
+when <i>name</i> information is unavailable or the envelope sender
+address is empty. This is the same behavior as prior to Postfix
+3.3. </p>
+
+<li> <p> In the <b>standard</b> form, the <i>name</i> will be quoted
+if it contains <b>specials</b> as defined in <a href="http://tools.ietf.org/html/rfc5322">RFC 5322</a>, or the "!%"
+address operators. </p>
+
+<li> <p> The Postfix <a href="sendmail.1.html">sendmail(1)</a> command gets <i>name</i> information
+from the <b>-F</b> command-line option, from the <b>NAME</b>
+environment variable, or from the UNIX password file. </p>
+
+</ul>
+
+<p> This feature is available in Postfix 3.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="header_size_limit">header_size_limit</a>
+(default: 102400)</b></DT><DD>
+
+<p>
+The maximal amount of memory in bytes for storing a message header.
+If a header is larger, the excess is discarded. The limit is
+enforced by the <a href="cleanup.8.html">cleanup(8)</a> server.
+</p>
+
+
+</DD>
+
+<DT><b><a name="helpful_warnings">helpful_warnings</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Log warnings about problematic configuration settings, and provide
+helpful suggestions.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="home_mailbox">home_mailbox</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional pathname of a mailbox file relative to a <a href="local.8.html">local(8)</a> user's
+home directory.
+</p>
+
+<p>
+Specify a pathname ending in "/" for qmail-style delivery.
+</p>
+
+<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
+is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
+<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
+<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. </p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#home_mailbox">home_mailbox</a> = Mailbox
+<a href="postconf.5.html#home_mailbox">home_mailbox</a> = Maildir/
+</pre>
+
+
+</DD>
+
+<DT><b><a name="hopcount_limit">hopcount_limit</a>
+(default: 50)</b></DT><DD>
+
+<p>
+The maximal number of Received: message headers that is allowed
+in the primary message headers. A message that exceeds the limit
+is bounced, in order to stop a mailer loop.
+</p>
+
+
+</DD>
+
+<DT><b><a name="html_directory">html_directory</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The location of Postfix HTML files that describe how to build,
+configure or operate a specific Postfix subsystem or feature.
+</p>
+
+
+</DD>
+
+<DT><b><a name="ignore_mx_lookup_error">ignore_mx_lookup_error</a>
+(default: no)</b></DT><DD>
+
+<p> Ignore DNS MX lookups that produce no response. By default,
+the Postfix SMTP client defers delivery and tries again after some
+delay. This behavior is required by the SMTP standard. </p>
+
+<p>
+Specify "<a href="postconf.5.html#ignore_mx_lookup_error">ignore_mx_lookup_error</a> = yes" to force a DNS A record
+lookup instead. This violates the SMTP standard and can result in
+mis-delivery of mail.
+</p>
+
+
+</DD>
+
+<DT><b><a name="import_environment">import_environment</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The list of environment parameters that a privileged Postfix
+process will import from a non-Postfix parent process, or name=value
+environment overrides. Unprivileged utilities will enforce the
+name=value overrides, but otherwise will not change their process
+environment. Examples of relevant parameters: </p>
+
+<dl>
+
+<dt><b>TZ</b></dt>
+
+<dd>May be needed for sane time keeping on most System-V-ish systems.
+</dd>
+
+<dt><b>DISPLAY</b></dt>
+
+<dd>Needed for debugging Postfix daemons with an X-windows debugger. </dd>
+
+<dt><b>XAUTHORITY</b></dt>
+
+<dd>Needed for debugging Postfix daemons with an X-windows debugger. </dd>
+
+<dt><b>MAIL_CONFIG</b></dt>
+
+<dd>Needed to make "<b>postfix -c</b>" work. </dd>
+
+</dl>
+
+<p> Specify a list of names and/or name=value pairs, separated by
+whitespace or comma. Specify "{ name=value }" to protect whitespace
+or comma in parameter values (whitespace after the opening "{" and
+before the closing "}"
+is ignored). The form name=value is supported with Postfix version
+2.1 and later; the use of {} is supported with Postfix 3.0 and
+later. </p>
+
+
+</DD>
+
+<DT><b><a name="in_flow_delay">in_flow_delay</a>
+(default: 1s)</b></DT><DD>
+
+<p> Time to pause before accepting a new message, when the message
+arrival rate exceeds the message delivery rate. This feature is
+turned on by default (it's disabled on SCO UNIX due to an SCO bug).
+</p>
+
+<p>
+With the default 100 Postfix SMTP server process limit, "<a href="postconf.5.html#in_flow_delay">in_flow_delay</a>
+= 1s" limits the mail inflow to 100 messages per second above the
+number of messages delivered per second.
+</p>
+
+<p>
+Specify 0 to disable the feature. Valid delays are 0..10.
+</p>
+
+
+</DD>
+
+<DT><b><a name="inet_interfaces">inet_interfaces</a>
+(default: all)</b></DT><DD>
+
+<p> The network interface addresses that this mail system receives
+mail on. Specify "all" to receive mail on all network
+interfaces (default), and "loopback-only" to receive mail
+on loopback network interfaces only (Postfix version 2.2 and later). The
+parameter also controls delivery of mail to <tt>user@[ip.address]</tt>.
+</p>
+
+<p>
+Note 1: you need to stop and start Postfix when this parameter changes.
+</p>
+
+<p> Note 2: address information may be enclosed inside <tt>[]</tt>,
+but this form is not required here. </p>
+
+<p> When <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> specifies just one IPv4 and/or IPv6 address
+that is not a loopback address, the Postfix SMTP client will use
+this address as the IP source address for outbound mail. Support
+for IPv6 is available in Postfix version 2.2 and later. </p>
+
+<p>
+On a multi-homed firewall with separate Postfix instances listening on the
+"inside" and "outside" interfaces, this can prevent each instance from
+being able to reach remote SMTP servers on the "other side" of the
+firewall. Setting
+<a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a> to 0.0.0.0 avoids the potential problem for
+IPv4, and setting <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a> to :: solves the problem
+for IPv6. </p>
+
+<p>
+A better solution for multi-homed firewalls is to leave <a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
+at the default value and instead use explicit IP addresses in
+the <a href="master.5.html">master.cf</a> SMTP server definitions. This preserves the Postfix
+SMTP client's
+loop detection, by ensuring that each side of the firewall knows that the
+other IP address is still the same host. Setting $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> to a
+single IPv4 and/or IPV6 address is primarily useful with virtual
+hosting of domains on
+secondary IP addresses, when each IP address serves a different domain
+(and has a different $<a href="postconf.5.html#myhostname">myhostname</a> setting). </p>
+
+<p>
+See also the <a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a> parameter, for network addresses that
+are forwarded to Postfix by way of a proxy or address translator.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = all (DEFAULT)
+<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = loopback-only (Postfix version 2.2 and later)
+<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = 127.0.0.1
+<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = 127.0.0.1, [::1] (Postfix version 2.2 and later)
+<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = 192.168.1.2, 127.0.0.1
+</pre>
+
+
+</DD>
+
+<DT><b><a name="inet_protocols">inet_protocols</a>
+(default: all)</b></DT><DD>
+
+<p> The Internet protocols Postfix will attempt to use when making
+or accepting connections. Specify one or more of "ipv4"
+or "ipv6", separated by whitespace or commas. The form
+"all" is equivalent to "ipv4, ipv6" or "ipv4", depending
+on whether the operating system implements IPv6. </p>
+
+<p> With Postfix 2.8 and earlier the default is "ipv4". For backwards
+compatibility with these releases, the Postfix 2.9 and later upgrade
+procedure appends an explicit "<a href="postconf.5.html#inet_protocols">inet_protocols</a> = ipv4" setting to
+<a href="postconf.5.html">main.cf</a> when no explicit setting is present. This compatibility
+workaround will be phased out as IPv6 deployment becomes more common.
+</p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+<p> Note: you MUST stop and start Postfix after changing this
+parameter. </p>
+
+<p> On systems that pre-date IPV6_V6ONLY support (<a href="http://tools.ietf.org/html/rfc3493">RFC 3493</a>), an
+IPv6 server will also accept IPv4 connections, even when IPv4 is
+turned off with the <a href="postconf.5.html#inet_protocols">inet_protocols</a> parameter. On systems with
+IPV6_V6ONLY support, Postfix will use separate server sockets for
+IPv6 and IPv4, and each will accept only connections for the
+corresponding protocol. </p>
+
+<p> When IPv4 support is enabled via the <a href="postconf.5.html#inet_protocols">inet_protocols</a> parameter,
+Postfix will look up DNS type A records, and will convert
+IPv4-in-IPv6 client IP addresses (::ffff:1.2.3.4) to their original
+IPv4 form (1.2.3.4). The latter is needed on hosts that pre-date
+IPV6_V6ONLY support (<a href="http://tools.ietf.org/html/rfc3493">RFC 3493</a>). </p>
+
+<p> When IPv6 support is enabled via the <a href="postconf.5.html#inet_protocols">inet_protocols</a> parameter,
+Postfix will do DNS type AAAA record lookups. </p>
+
+<p> When both IPv4 and IPv6 support are enabled, the Postfix SMTP
+client will choose the protocol as specified with the
+<a href="postconf.5.html#smtp_address_preference">smtp_address_preference</a> parameter. Postfix versions before 2.8
+attempt to connect via IPv6 before attempting to use IPv4. </p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#inet_protocols">inet_protocols</a> = ipv4
+<a href="postconf.5.html#inet_protocols">inet_protocols</a> = all (DEFAULT)
+<a href="postconf.5.html#inet_protocols">inet_protocols</a> = ipv6
+<a href="postconf.5.html#inet_protocols">inet_protocols</a> = ipv4, ipv6
+</pre>
+
+
+</DD>
+
+<DT><b><a name="initial_destination_concurrency">initial_destination_concurrency</a>
+(default: 5)</b></DT><DD>
+
+<p>
+The initial per-destination concurrency level for parallel delivery
+to the same destination.
+With per-destination recipient limit &gt; 1, a destination is a domain,
+otherwise it is a recipient.
+</p>
+
+<p> Use <a href="postconf.5.html#transport_initial_destination_concurrency"><i>transport</i>_initial_destination_concurrency</a> to specify
+a transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
+name of the message delivery transport (Postfix 2.5 and later). </p>
+
+<p>
+Warning: with concurrency of 1, one bad message can be enough to
+block all mail to a site.
+</p>
+
+
+</DD>
+
+<DT><b><a name="internal_mail_filter_classes">internal_mail_filter_classes</a>
+(default: empty)</b></DT><DD>
+
+<p> What categories of Postfix-generated mail are subject to
+before-queue content inspection by <a href="postconf.5.html#non_smtpd_milters">non_smtpd_milters</a>, <a href="postconf.5.html#header_checks">header_checks</a>
+and <a href="postconf.5.html#body_checks">body_checks</a>. Specify zero or more of the following, separated
+by whitespace or comma. </p>
+
+<dl>
+
+<dt><b>bounce</b></dt> <dd> Inspect the content of delivery
+status notifications. </dd>
+
+<dt><b>notify</b></dt> <dd> Inspect the content of postmaster
+notifications by the <a href="smtp.8.html">smtp(8)</a> and <a href="smtpd.8.html">smtpd(8)</a> processes. </dd>
+
+</dl>
+
+<p> NOTE: It's generally not safe to enable content inspection of
+Postfix-generated email messages. The user is warned. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="invalid_hostname_reject_code">invalid_hostname_reject_code</a>
+(default: 501)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code when the client
+HELO or EHLO command parameter is rejected by the <a href="postconf.5.html#reject_invalid_helo_hostname">reject_invalid_helo_hostname</a>
+restriction.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="ipc_idle">ipc_idle</a>
+(default: version dependent)</b></DT><DD>
+
+<p>
+The time after which a client closes an idle internal communication
+channel. The purpose is to allow Postfix daemon processes to
+terminate voluntarily after they become idle. This is used, for
+example, by the Postfix address resolving and rewriting clients.
+</p>
+
+<p> With Postfix 2.4 the default value was reduced from 100s to 5s. </p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="ipc_timeout">ipc_timeout</a>
+(default: 3600s)</b></DT><DD>
+
+<p>
+The time limit for sending or receiving information over an internal
+communication channel. The purpose is to break out of deadlock
+situations. If the time limit is exceeded the software aborts with a
+fatal error.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="ipc_ttl">ipc_ttl</a>
+(default: 1000s)</b></DT><DD>
+
+<p>
+The time after which a client closes an active internal communication
+channel. The purpose is to allow Postfix daemon processes to
+terminate voluntarily
+after reaching their client limit. This is used, for example, by
+the Postfix address resolving and rewriting clients.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="line_length_limit">line_length_limit</a>
+(default: 2048)</b></DT><DD>
+
+<p> Upon input, long lines are chopped up into pieces of at most
+this length; upon delivery, long lines are reconstructed. </p>
+
+
+</DD>
+
+<DT><b><a name="lmdb_map_size">lmdb_map_size</a>
+(default: 16777216)</b></DT><DD>
+
+<p>
+The initial OpenLDAP LMDB database size limit in bytes. Each time
+a database becomes full, its size limit is doubled.
+</p>
+
+<p>
+This feature is available in Postfix 2.11 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_address_preference">lmtp_address_preference</a>
+(default: ipv6)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_address_preference">smtp_address_preference</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_address_verify_target">lmtp_address_verify_target</a>
+(default: rcpt)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_address_verify_target">smtp_address_verify_target</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_assume_final">lmtp_assume_final</a>
+(default: no)</b></DT><DD>
+
+<p> When a remote LMTP server announces no DSN support, assume that
+the
+server performs final delivery, and send "delivered" delivery status
+notifications instead of "relayed". The default setting is backwards
+compatible to avoid the infinitesimal possibility of breaking
+existing LMTP-based content filters. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_balance_inet_protocols">lmtp_balance_inet_protocols</a>
+(default: yes)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_balance_inet_protocols">smtp_balance_inet_protocols</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 3.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_bind_address">lmtp_bind_address</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_bind_address6">lmtp_bind_address6</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_body_checks">lmtp_body_checks</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_body_checks">smtp_body_checks</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_cache_connection">lmtp_cache_connection</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Keep Postfix LMTP client connections open for up to $<a href="postconf.5.html#max_idle">max_idle</a>
+seconds. When the LMTP client receives a request for the same
+connection the connection is reused.
+</p>
+
+<p> This parameter is available in Postfix version 2.2 and earlier.
+With Postfix version 2.3 and later, see <a href="postconf.5.html#lmtp_connection_cache_on_demand">lmtp_connection_cache_on_demand</a>,
+<a href="postconf.5.html#lmtp_connection_cache_destinations">lmtp_connection_cache_destinations</a>, or <a href="postconf.5.html#lmtp_connection_reuse_time_limit">lmtp_connection_reuse_time_limit</a>.
+</p>
+
+<p>
+The effectiveness of cached connections will be determined by the
+number of remote LMTP servers in use, and the concurrency limit specified
+for the Postfix LMTP client. Cached connections are closed under any of
+the following conditions:
+</p>
+
+<ul>
+
+<li> The Postfix LMTP client idle time limit is reached. This limit is
+specified with the Postfix <a href="postconf.5.html#max_idle">max_idle</a> configuration parameter.
+
+<li> A delivery request specifies a different destination than the
+one currently cached.
+
+<li> The per-process limit on the number of delivery requests is
+reached. This limit is specified with the Postfix <a href="postconf.5.html#max_use">max_use</a>
+configuration parameter.
+
+<li> Upon the onset of another delivery request, the remote LMTP server
+associated with the current session does not respond to the RSET
+command.
+
+</ul>
+
+<p>
+Most of these limitations have been with the Postfix
+a connection cache that is shared among multiple LMTP client
+programs.
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_cname_overrides_servername">lmtp_cname_overrides_servername</a>
+(default: yes)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_cname_overrides_servername">smtp_cname_overrides_servername</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_connect_timeout">lmtp_connect_timeout</a>
+(default: 0s)</b></DT><DD>
+
+<p> The Postfix LMTP client time limit for completing a TCP connection, or
+zero (use the operating system built-in time limit). When no
+connection can be made within the deadline, the LMTP client tries
+the next address on the mail exchanger list. </p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#lmtp_connect_timeout">lmtp_connect_timeout</a> = 30s
+</pre>
+
+
+</DD>
+
+<DT><b><a name="lmtp_connection_cache_destinations">lmtp_connection_cache_destinations</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_connection_cache_destinations">smtp_connection_cache_destinations</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_connection_cache_on_demand">lmtp_connection_cache_on_demand</a>
+(default: yes)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_connection_cache_on_demand">smtp_connection_cache_on_demand</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_connection_cache_time_limit">lmtp_connection_cache_time_limit</a>
+(default: 2s)</b></DT><DD>
+
+<p> The LMTP-specific version of the
+<a href="postconf.5.html#smtp_connection_cache_time_limit">smtp_connection_cache_time_limit</a> configuration parameter.
+See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_connection_reuse_count_limit">lmtp_connection_reuse_count_limit</a>
+(default: 0)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_connection_reuse_count_limit">smtp_connection_reuse_count_limit</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.11 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_connection_reuse_time_limit">lmtp_connection_reuse_time_limit</a>
+(default: 300s)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_connection_reuse_time_limit">smtp_connection_reuse_time_limit</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_data_done_timeout">lmtp_data_done_timeout</a>
+(default: 600s)</b></DT><DD>
+
+<p> The Postfix LMTP client time limit for sending the LMTP ".",
+and for receiving the remote LMTP server response. When no response
+is received within the deadline, a warning is logged that the mail
+may be delivered multiple times. </p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_data_init_timeout">lmtp_data_init_timeout</a>
+(default: 120s)</b></DT><DD>
+
+<p>
+The Postfix LMTP client time limit for sending the LMTP DATA command,
+and
+for receiving the remote LMTP server response.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_data_xfer_timeout">lmtp_data_xfer_timeout</a>
+(default: 180s)</b></DT><DD>
+
+<p>
+The Postfix LMTP client time limit for sending the LMTP message
+content.
+When the connection stalls for more than $<a href="postconf.5.html#lmtp_data_xfer_timeout">lmtp_data_xfer_timeout</a>
+the LMTP client terminates the transfer.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_defer_if_no_mx_address_found">lmtp_defer_if_no_mx_address_found</a>
+(default: no)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_defer_if_no_mx_address_found">smtp_defer_if_no_mx_address_found</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_delivery_status_filter">lmtp_delivery_status_filter</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_delivery_status_filter">smtp_delivery_status_filter</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_destination_concurrency_limit">lmtp_destination_concurrency_limit</a>
+(default: $<a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a>)</b></DT><DD>
+
+<p> The maximal number of parallel deliveries to the same destination
+via the lmtp message delivery transport. This limit is enforced by
+the queue manager. The message delivery transport name is the first
+field in the entry in the <a href="master.5.html">master.cf</a> file. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_destination_recipient_limit">lmtp_destination_recipient_limit</a>
+(default: $<a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a>)</b></DT><DD>
+
+<p> The maximal number of recipients per message for the lmtp
+message delivery transport. This limit is enforced by the queue
+manager. The message delivery transport name is the first field in
+the entry in the <a href="master.5.html">master.cf</a> file. </p>
+
+<p> Setting this parameter to a value of 1 changes the meaning of
+<a href="postconf.5.html#lmtp_destination_concurrency_limit">lmtp_destination_concurrency_limit</a> from concurrency per domain into
+concurrency per recipient. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_discard_lhlo_keyword_address_maps">lmtp_discard_lhlo_keyword_address_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Lookup tables, indexed by the remote LMTP server address, with
+case insensitive lists of LHLO keywords (pipelining, starttls,
+auth, etc.) that the Postfix LMTP client will ignore in the LHLO
+response
+from a remote LMTP server. See <a href="postconf.5.html#lmtp_discard_lhlo_keywords">lmtp_discard_lhlo_keywords</a> for
+details. The table is not indexed by hostname for consistency with
+<a href="postconf.5.html#smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a>. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_discard_lhlo_keywords">lmtp_discard_lhlo_keywords</a>
+(default: empty)</b></DT><DD>
+
+<p> A case insensitive list of LHLO keywords (pipelining, starttls,
+auth, etc.) that the Postfix LMTP client will ignore in the LHLO
+response
+from a remote LMTP server. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+<p> Notes: </p>
+
+<ul>
+
+<li> <p> Specify the <b>silent-discard</b> pseudo keyword to prevent
+this action from being logged. </p>
+
+<li> <p> Use the <a href="postconf.5.html#lmtp_discard_lhlo_keyword_address_maps">lmtp_discard_lhlo_keyword_address_maps</a> feature to
+discard LHLO keywords selectively. </p>
+
+</ul>
+
+
+</DD>
+
+<DT><b><a name="lmtp_dns_reply_filter">lmtp_dns_reply_filter</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional filter for Postfix LMTP client DNS lookup results.
+See <a href="postconf.5.html#smtp_dns_reply_filter">smtp_dns_reply_filter</a> for details including an example. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_dns_resolver_options">lmtp_dns_resolver_options</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_dns_resolver_options">smtp_dns_resolver_options</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_dns_support_level">lmtp_dns_support_level</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_dns_support_level">smtp_dns_support_level</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.11 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_enforce_tls">lmtp_enforce_tls</a>
+(default: no)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_fallback_relay">lmtp_fallback_relay</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional list of relay hosts for LMTP destinations that can't be
+found or that are unreachable. In <a href="postconf.5.html">main.cf</a> elements are separated by
+whitespace or commas. </p>
+
+<p> By default, mail is returned to the sender when a destination is not
+found, and delivery is deferred when a destination is unreachable. </p>
+
+<p> The fallback relays must be TCP destinations, specified without
+a leading "inet:" prefix. Specify a host or host:port. Since MX
+lookups do not apply with LMTP, there is no need to use the "[host]" or
+"[host]:port" forms. If you specify multiple LMTP destinations, Postfix
+will try them in the specified order. </p>
+
+<p>
+This feature is available in Postfix 3.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_generic_maps">lmtp_generic_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_generic_maps">smtp_generic_maps</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_header_checks">lmtp_header_checks</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_header_checks">smtp_header_checks</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_host_lookup">lmtp_host_lookup</a>
+(default: dns)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_host_lookup">smtp_host_lookup</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_lhlo_name">lmtp_lhlo_name</a>
+(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</b></DT><DD>
+
+<p>
+The hostname to send in the LMTP LHLO command.
+</p>
+
+<p>
+The default value is the machine hostname. Specify a hostname or
+[ip.add.re.ss].
+</p>
+
+<p>
+This information can be specified in the <a href="postconf.5.html">main.cf</a> file for all LMTP
+clients, or it can be specified in the <a href="master.5.html">master.cf</a> file for a specific
+client, for example:
+</p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="master.5.html">master.cf</a>:
+ mylmtp ... lmtp -o <a href="postconf.5.html#lmtp_lhlo_name">lmtp_lhlo_name</a>=foo.bar.com
+</pre>
+</blockquote>
+
+<p>
+This feature is available in Postfix 2.3 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_lhlo_timeout">lmtp_lhlo_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p> The Postfix LMTP client time limit for sending the LHLO command,
+and for receiving the initial remote LMTP server response. </p>
+
+<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
+(weeks). The default time unit is s (seconds). </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_line_length_limit">lmtp_line_length_limit</a>
+(default: 990)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_line_length_limit">smtp_line_length_limit</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_mail_timeout">lmtp_mail_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The Postfix LMTP client time limit for sending the MAIL FROM command,
+and for receiving the remote LMTP server response.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_mime_header_checks">lmtp_mime_header_checks</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_mime_header_checks">smtp_mime_header_checks</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_mx_address_limit">lmtp_mx_address_limit</a>
+(default: 5)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_mx_address_limit">smtp_mx_address_limit</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_mx_session_limit">lmtp_mx_session_limit</a>
+(default: 2)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_mx_session_limit">smtp_mx_session_limit</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_nested_header_checks">lmtp_nested_header_checks</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_nested_header_checks">smtp_nested_header_checks</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_per_record_deadline">lmtp_per_record_deadline</a>
+(default: no)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_per_record_deadline">smtp_per_record_deadline</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.9 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_pix_workaround_delay_time">lmtp_pix_workaround_delay_time</a>
+(default: 10s)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_pix_workaround_delay_time">smtp_pix_workaround_delay_time</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_pix_workaround_maps">lmtp_pix_workaround_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_pix_workaround_maps">smtp_pix_workaround_maps</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_pix_workaround_threshold_time">lmtp_pix_workaround_threshold_time</a>
+(default: 500s)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_pix_workaround_threshold_time">smtp_pix_workaround_threshold_time</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_pix_workarounds">lmtp_pix_workarounds</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the smtp_pix_workaround
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_quit_timeout">lmtp_quit_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The Postfix LMTP client time limit for sending the QUIT command,
+and for receiving the remote LMTP server response.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_quote_rfc821_envelope">lmtp_quote_rfc821_envelope</a>
+(default: yes)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_quote_rfc821_envelope">smtp_quote_rfc821_envelope</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_randomize_addresses">lmtp_randomize_addresses</a>
+(default: yes)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_randomize_addresses">smtp_randomize_addresses</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_rcpt_timeout">lmtp_rcpt_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The Postfix LMTP client time limit for sending the RCPT TO command,
+and for receiving the remote LMTP server response.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_reply_filter">lmtp_reply_filter</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_reply_filter">smtp_reply_filter</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.7 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_rset_timeout">lmtp_rset_timeout</a>
+(default: 20s)</b></DT><DD>
+
+<p> The Postfix LMTP client time limit for sending the RSET command,
+and for receiving the remote LMTP server response. The LMTP client
+sends RSET in
+order to finish a recipient address probe, or to verify that a
+cached connection is still alive. </p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_sasl_auth_cache_name">lmtp_sasl_auth_cache_name</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_sasl_auth_cache_time">lmtp_sasl_auth_cache_time</a>
+(default: 90d)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_auth_cache_time">smtp_sasl_auth_cache_time</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_sasl_auth_enable">lmtp_sasl_auth_enable</a>
+(default: no)</b></DT><DD>
+
+<p>
+Enable SASL authentication in the Postfix LMTP client.
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_sasl_auth_soft_bounce">lmtp_sasl_auth_soft_bounce</a>
+(default: yes)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_sasl_mechanism_filter">lmtp_sasl_mechanism_filter</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_sasl_password_maps">lmtp_sasl_password_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional Postfix LMTP client lookup tables with one username:password entry
+per host or domain. If a remote host or domain has no username:password
+entry, then the Postfix LMTP client will not attempt to authenticate
+to the remote host.
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_sasl_path">lmtp_sasl_path</a>
+(default: empty)</b></DT><DD>
+
+<p> Implementation-specific information that is passed through to
+the SASL plug-in implementation that is selected with
+<b><a href="postconf.5.html#lmtp_sasl_type">lmtp_sasl_type</a></b>. Typically this specifies the name of a
+configuration file or rendezvous point. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_sasl_security_options">lmtp_sasl_security_options</a>
+(default: noplaintext, noanonymous)</b></DT><DD>
+
+<p> SASL security options; as of Postfix 2.3 the list of available
+features depends on the SASL client implementation that is selected
+with <b><a href="postconf.5.html#lmtp_sasl_type">lmtp_sasl_type</a></b>. </p>
+
+<p> The following security features are defined for the <b>cyrus</b>
+client SASL implementation: </p>
+
+<dl>
+
+<dt><b>noplaintext</b></dt>
+
+<dd>Disallow authentication methods that use plaintext passwords. </dd>
+
+<dt><b>noactive</b></dt>
+
+<dd>Disallow authentication methods that are vulnerable to non-dictionary
+active attacks. </dd>
+
+<dt><b>nodictionary</b></dt>
+
+<dd>Disallow authentication methods that are vulnerable to passive
+dictionary attack. </dd>
+
+<dt><b>noanonymous</b></dt>
+
+<dd>Disallow anonymous logins. </dd>
+
+</dl>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#lmtp_sasl_security_options">lmtp_sasl_security_options</a> = noplaintext
+</pre>
+
+
+</DD>
+
+<DT><b><a name="lmtp_sasl_tls_security_options">lmtp_sasl_tls_security_options</a>
+(default: $<a href="postconf.5.html#lmtp_sasl_security_options">lmtp_sasl_security_options</a>)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_tls_security_options">smtp_sasl_tls_security_options</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_sasl_tls_verified_security_options">lmtp_sasl_tls_verified_security_options</a>
+(default: $<a href="postconf.5.html#lmtp_sasl_tls_security_options">lmtp_sasl_tls_security_options</a>)</b></DT><DD>
+
+<p> The LMTP-specific version of the
+<a href="postconf.5.html#smtp_sasl_tls_verified_security_options">smtp_sasl_tls_verified_security_options</a> configuration parameter.
+See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_sasl_type">lmtp_sasl_type</a>
+(default: cyrus)</b></DT><DD>
+
+<p> The SASL plug-in type that the Postfix LMTP client should use
+for authentication. The available types are listed with the
+"<b>postconf -A</b>" command. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_send_dummy_mail_auth">lmtp_send_dummy_mail_auth</a>
+(default: no)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_send_dummy_mail_auth">smtp_send_dummy_mail_auth</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.9 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_send_xforward_command">lmtp_send_xforward_command</a>
+(default: no)</b></DT><DD>
+
+<p>
+Send an XFORWARD command to the remote LMTP server when the LMTP LHLO
+server response announces XFORWARD support. This allows an <a href="lmtp.8.html">lmtp(8)</a>
+delivery agent, used for content filter message injection, to
+forward the name, address, protocol and HELO name of the original
+client to the content filter and downstream queuing LMTP server.
+Before you change the value to yes, it is best to make sure that
+your content filter supports this command.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_sender_dependent_authentication">lmtp_sender_dependent_authentication</a>
+(default: no)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_sender_dependent_authentication">smtp_sender_dependent_authentication</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_skip_5xx_greeting">lmtp_skip_5xx_greeting</a>
+(default: yes)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_skip_5xx_greeting">smtp_skip_5xx_greeting</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_skip_quit_response">lmtp_skip_quit_response</a>
+(default: no)</b></DT><DD>
+
+<p>
+Wait for the response to the LMTP QUIT command.
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_starttls_timeout">lmtp_starttls_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_starttls_timeout">smtp_starttls_timeout</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tcp_port">lmtp_tcp_port</a>
+(default: 24)</b></DT><DD>
+
+<p>
+The default TCP port that the Postfix LMTP client connects to.
+Specify a symbolic name (see services(5)) or a numeric port.
+</p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_CAfile">lmtp_tls_CAfile</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_CApath">lmtp_tls_CApath</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_CApath">smtp_tls_CApath</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_block_early_mail_reply">lmtp_tls_block_early_mail_reply</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_block_early_mail_reply">smtp_tls_block_early_mail_reply</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.7 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_cert_file">lmtp_tls_cert_file</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_chain_files">lmtp_tls_chain_files</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_ciphers">lmtp_tls_ciphers</a>
+(default: medium)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_ciphers">smtp_tls_ciphers</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_connection_reuse">lmtp_tls_connection_reuse</a>
+(default: no)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_connection_reuse">smtp_tls_connection_reuse</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_dcert_file">lmtp_tls_dcert_file</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_dkey_file">lmtp_tls_dkey_file</a>
+(default: $<a href="postconf.5.html#lmtp_tls_dcert_file">lmtp_tls_dcert_file</a>)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_dkey_file">smtp_tls_dkey_file</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_eccert_file">lmtp_tls_eccert_file</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.6 and later, when Postfix is
+compiled and linked with OpenSSL 1.0.0 or later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_eckey_file">lmtp_tls_eckey_file</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_eckey_file">smtp_tls_eckey_file</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.6 and later, when Postfix is
+compiled and linked with OpenSSL 1.0.0 or later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_enforce_peername">lmtp_tls_enforce_peername</a>
+(default: yes)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_exclude_ciphers">lmtp_tls_exclude_ciphers</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_fingerprint_cert_match">lmtp_tls_fingerprint_cert_match</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_fingerprint_digest">lmtp_tls_fingerprint_digest</a>
+(default: md5)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_force_insecure_host_tlsa_lookup">lmtp_tls_force_insecure_host_tlsa_lookup</a>
+(default: no)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_force_insecure_host_tlsa_lookup">smtp_tls_force_insecure_host_tlsa_lookup</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.11 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_key_file">lmtp_tls_key_file</a>
+(default: $<a href="postconf.5.html#lmtp_tls_cert_file">lmtp_tls_cert_file</a>)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_key_file">smtp_tls_key_file</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_loglevel">lmtp_tls_loglevel</a>
+(default: 0)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_loglevel">smtp_tls_loglevel</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_mandatory_ciphers">lmtp_tls_mandatory_ciphers</a>
+(default: medium)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_mandatory_exclude_ciphers">lmtp_tls_mandatory_exclude_ciphers</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_mandatory_exclude_ciphers">smtp_tls_mandatory_exclude_ciphers</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_mandatory_protocols">lmtp_tls_mandatory_protocols</a>
+(default: !SSLv2, !SSLv3)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_note_starttls_offer">lmtp_tls_note_starttls_offer</a>
+(default: no)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_note_starttls_offer">smtp_tls_note_starttls_offer</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_per_site">lmtp_tls_per_site</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_policy_maps">lmtp_tls_policy_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_protocols">lmtp_tls_protocols</a>
+(default: !SSLv2, !SSLv3)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_protocols">smtp_tls_protocols</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_scert_verifydepth">lmtp_tls_scert_verifydepth</a>
+(default: 9)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_scert_verifydepth">smtp_tls_scert_verifydepth</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_secure_cert_match">lmtp_tls_secure_cert_match</a>
+(default: nexthop)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_security_level">lmtp_tls_security_level</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_servername">lmtp_tls_servername</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_servername">smtp_tls_servername</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_session_cache_database">lmtp_tls_session_cache_database</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_session_cache_database">smtp_tls_session_cache_database</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_session_cache_timeout">lmtp_tls_session_cache_timeout</a>
+(default: 3600s)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_session_cache_timeout">smtp_tls_session_cache_timeout</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_trust_anchor_file">lmtp_tls_trust_anchor_file</a>
+(default: empty)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_trust_anchor_file">smtp_tls_trust_anchor_file</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.11 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_tls_verify_cert_match">lmtp_tls_verify_cert_match</a>
+(default: hostname)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a>
+configuration parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_use_tls">lmtp_use_tls</a>
+(default: no)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a> configuration
+parameter. See there for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="lmtp_xforward_timeout">lmtp_xforward_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The Postfix LMTP client time limit for sending the XFORWARD command,
+and for receiving the remote LMTP server response.
+</p>
+
+<p>
+In case of problems the client does NOT try the next address on
+the mail exchanger list.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="local_command_shell">local_command_shell</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional shell program for <a href="local.8.html">local(8)</a> delivery to non-Postfix command.
+By default, non-Postfix commands are executed directly; commands
+are given to given to the default shell (typically, /bin/sh) only
+when they contain shell meta characters or shell built-in commands.
+</p>
+
+<p> "sendmail's restricted shell" (smrsh) is what most people will
+use in order to restrict what programs can be run from e.g. .forward
+files (smrsh is part of the Sendmail distribution). </p>
+
+<p> Note: when a shell program is specified, it is invoked even
+when the command contains no shell built-in commands or meta
+characters. </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#local_command_shell">local_command_shell</a> = /some/where/smrsh -c
+<a href="postconf.5.html#local_command_shell">local_command_shell</a> = /bin/bash -c
+</pre>
+
+
+</DD>
+
+<DT><b><a name="local_delivery_status_filter">local_delivery_status_filter</a>
+(default: $<a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a>)</b></DT><DD>
+
+<p> Optional filter for the <a href="local.8.html">local(8)</a> delivery agent to change the
+status code or explanatory text of successful or unsuccessful
+deliveries. See <a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a> for details. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="local_destination_concurrency_limit">local_destination_concurrency_limit</a>
+(default: 2)</b></DT><DD>
+
+<p> The maximal number of parallel deliveries via the local mail
+delivery transport to the same recipient (when
+"<a href="postconf.5.html#local_destination_recipient_limit">local_destination_recipient_limit</a> = 1") or the maximal number of
+parallel deliveries to the same <a href="ADDRESS_CLASS_README.html#local_domain_class">local domain</a> (when
+"<a href="postconf.5.html#local_destination_recipient_limit">local_destination_recipient_limit</a> &gt; 1"). This limit is enforced by
+the queue manager. The message delivery transport name is the first
+field in the entry in the <a href="master.5.html">master.cf</a> file. </p>
+
+<p> A low limit of 2 is recommended, just in case someone has an
+expensive shell command in a .forward file or in an alias (e.g.,
+a mailing list manager). You don't want to run lots of those at
+the same time. </p>
+
+
+</DD>
+
+<DT><b><a name="local_destination_recipient_limit">local_destination_recipient_limit</a>
+(default: 1)</b></DT><DD>
+
+<p> The maximal number of recipients per message delivery via the
+local mail delivery transport. This limit is enforced by the queue
+manager. The message delivery transport name is the first field in
+the entry in the <a href="master.5.html">master.cf</a> file. </p>
+
+<p> Setting this parameter to a value &gt; 1 changes the meaning of
+<a href="postconf.5.html#local_destination_concurrency_limit">local_destination_concurrency_limit</a> from concurrency per recipient
+into concurrency per domain. </p>
+
+
+</DD>
+
+<DT><b><a name="local_header_rewrite_clients">local_header_rewrite_clients</a>
+(default: <a href="postconf.5.html#permit_inet_interfaces">permit_inet_interfaces</a>)</b></DT><DD>
+
+<p> Rewrite message header addresses in mail from these clients and
+update incomplete addresses with the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or
+$<a href="postconf.5.html#mydomain">mydomain</a>; either don't rewrite message headers from other clients
+at all, or rewrite message headers and update incomplete addresses
+with the domain specified in the <a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a>
+parameter. </p>
+
+<p> See the <a href="postconf.5.html#append_at_myorigin">append_at_myorigin</a> and <a href="postconf.5.html#append_dot_mydomain">append_dot_mydomain</a> parameters
+for details of how domain names are appended to incomplete addresses.
+</p>
+
+<p> Specify a list of zero or more of the following: </p>
+
+<dl>
+
+<dt><b><a href="postconf.5.html#permit_inet_interfaces">permit_inet_interfaces</a></b></dt>
+
+<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
+client IP address matches $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>. This is enabled by
+default. </dd>
+
+<dt><b><a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a></b></dt>
+
+<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
+client IP address matches any network or network address listed in
+$<a href="postconf.5.html#mynetworks">mynetworks</a>. This setting will not prevent remote mail header
+address rewriting when mail from a remote client is forwarded by
+a neighboring system. </dd>
+
+<dt><b><a href="postconf.5.html#permit_sasl_authenticated">permit_sasl_authenticated</a> </b></dt>
+
+<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
+client is successfully authenticated via the <a href="http://tools.ietf.org/html/rfc4954">RFC 4954</a> (AUTH)
+protocol. </dd>
+
+<dt><b><a href="postconf.5.html#permit_tls_clientcerts">permit_tls_clientcerts</a> </b></dt>
+
+<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
+remote SMTP client TLS certificate fingerprint or public key fingerprint
+(Postfix 2.9 and later) is listed in $<a href="postconf.5.html#relay_clientcerts">relay_clientcerts</a>.
+The fingerprint digest algorithm is configurable via the
+<a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> parameter (hard-coded as md5 prior to
+Postfix version 2.5). </dd>
+
+<dt><b><a href="postconf.5.html#permit_tls_all_clientcerts">permit_tls_all_clientcerts</a> </b></dt>
+
+<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
+remote SMTP client TLS certificate is successfully verified, regardless of
+whether it is listed on the server, and regardless of the certifying
+authority. </dd>
+
+<dt><b><a name="check_address_map">check_address_map</a> <i><a href="DATABASE_README.html">type:table</a></i> </b></dt>
+
+<dt><b><i><a href="DATABASE_README.html">type:table</a></i> </b></dt>
+
+<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
+client IP address matches the specified lookup table.
+The lookup result is ignored, and no subnet lookup is done. This
+is suitable for, e.g., pop-before-smtp lookup tables. </dd>
+
+</dl>
+
+<p> Examples: </p>
+
+<p> The Postfix &lt; 2.2 backwards compatible setting: always rewrite
+message headers, and always append my own domain to incomplete
+header addresses. </p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all
+</pre>
+</blockquote>
+
+<p> The purist (and default) setting: rewrite headers only in mail
+from Postfix sendmail and in SMTP mail from this machine. </p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="postconf.5.html#permit_inet_interfaces">permit_inet_interfaces</a>
+</pre>
+</blockquote>
+
+<p> The intermediate setting: rewrite header addresses and append
+$<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> information only with mail from Postfix
+sendmail, from local clients, or from authorized SMTP clients. </p>
+
+<p> Note: this setting will not prevent remote mail header address
+rewriting when mail from a remote client is forwarded by a neighboring
+system. </p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>,
+ <a href="postconf.5.html#permit_sasl_authenticated">permit_sasl_authenticated</a> <a href="postconf.5.html#permit_tls_clientcerts">permit_tls_clientcerts</a>
+ <a href="postconf.5.html#check_address_map">check_address_map</a> <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/pop-before-smtp
+</pre>
+</blockquote>
+
+
+</DD>
+
+<DT><b><a name="local_recipient_maps">local_recipient_maps</a>
+(default: <a href="proxymap.8.html">proxy</a>:unix:passwd.byname $<a href="postconf.5.html#alias_maps">alias_maps</a>)</b></DT><DD>
+
+<p> Lookup tables with all names or addresses of local recipients:
+a recipient address is local when its domain matches $<a href="postconf.5.html#mydestination">mydestination</a>,
+$<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>. Specify @domain as a
+wild-card for domains that do not have a valid recipient list.
+Technically, tables listed with $<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> are used as
+lists: Postfix needs to know only if a lookup string is found or
+not, but it does not use the result from table lookup. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p>
+If this parameter is non-empty (the default), then the Postfix SMTP
+server will reject mail for unknown local users.
+</p>
+
+<p>
+To turn off local recipient checking in the Postfix SMTP server,
+specify "<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> =" (i.e. empty).
+</p>
+
+<p>
+The default setting assumes that you use the default Postfix local
+delivery agent for local delivery. You need to update the
+<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> setting if:
+</p>
+
+<ul>
+
+<li>You redefine the local delivery agent in <a href="master.5.html">master.cf</a>.
+
+<li>You redefine the "<a href="postconf.5.html#local_transport">local_transport</a>" setting in <a href="postconf.5.html">main.cf</a>.
+
+<li>You use the "<a href="postconf.5.html#luser_relay">luser_relay</a>", "<a href="postconf.5.html#mailbox_transport">mailbox_transport</a>", or "<a href="postconf.5.html#fallback_transport">fallback_transport</a>"
+feature of the Postfix <a href="local.8.html">local(8)</a> delivery agent.
+
+</ul>
+
+<p>
+Details are described in the <a href="LOCAL_RECIPIENT_README.html">LOCAL_RECIPIENT_README</a> file.
+</p>
+
+<p>
+Beware: if the Postfix SMTP server runs chrooted, you need to access
+the passwd file via the <a href="proxymap.8.html">proxymap(8)</a> service, in order to overcome
+chroot access restrictions. The alternative, maintaining a copy of
+the system password file in the chroot jail is not practical.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> =
+</pre>
+
+
+</DD>
+
+<DT><b><a name="local_transport">local_transport</a>
+(default: <a href="local.8.html">local</a>:$<a href="postconf.5.html#myhostname">myhostname</a>)</b></DT><DD>
+
+<p> The default mail delivery transport and next-hop destination
+for final delivery to domains listed with <a href="postconf.5.html#mydestination">mydestination</a>, and for
+[ipaddress] destinations that match $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.
+This information can be overruled with the <a href="transport.5.html">transport(5)</a> table. </p>
+
+<p>
+By default, local mail is delivered to the transport called "local",
+which is just the name of a service that is defined the <a href="master.5.html">master.cf</a> file.
+</p>
+
+<p>
+Specify a string of the form <i>transport:nexthop</i>, where <i>transport</i>
+is the name of a mail delivery transport defined in <a href="master.5.html">master.cf</a>.
+The <i>:nexthop</i> destination is optional; its syntax is documented
+in the manual page of the corresponding delivery agent.
+</p>
+
+<p>
+Beware: if you override the default local delivery agent then you
+need to review the <a href="LOCAL_RECIPIENT_README.html">LOCAL_RECIPIENT_README</a> document, otherwise the
+SMTP server may reject mail for local recipients.
+</p>
+
+
+</DD>
+
+<DT><b><a name="luser_relay">luser_relay</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional catch-all destination for unknown <a href="local.8.html">local(8)</a> recipients.
+By default, mail for unknown recipients in domains that match
+$<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a> is returned
+as undeliverable.
+</p>
+
+<p>
+The <a href="postconf.5.html#luser_relay">luser_relay</a> value is not subject to Postfix configuration
+parameter $name expansion. Instead, the following $name expansions
+are done:
+</p>
+
+<dl>
+
+<dt><b>$domain</b></dt>
+
+<dd>The recipient domain. </dd>
+
+<dt><b>$extension</b></dt>
+
+<dd>The recipient address extension. </dd>
+
+<dt><b>$home</b></dt>
+
+<dd>The recipient's home directory. </dd>
+
+<dt><b>$local</b></dt>
+
+<dd>The entire recipient address localpart. </dd>
+
+<dt><b>$recipient</b></dt>
+
+<dd>The full recipient address. </dd>
+
+<dt><b>$<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a></b></dt>
+
+<dd>The address extension delimiter that was found in the recipient
+address (Postfix 2.11 and later), or the system-wide recipient
+address extension delimiter (Postfix 2.10 and earlier). </dd>
+
+<dt><b>$shell</b></dt>
+
+<dd>The recipient's login shell. </dd>
+
+<dt><b>$user</b></dt>
+
+<dd>The recipient username. </dd>
+
+<dt><b>${name?value}</b></dt>
+
+<dd>Expands to <i>value</i> when <i>$name</i> has a non-empty value. </dd>
+
+<dt><b>${name:value}</b></dt>
+
+<dd>Expands to <i>value</i> when <i>$name</i> has an empty value. </dd>
+
+</dl>
+
+<p>
+Instead of $name you can also specify ${name} or $(name).
+</p>
+
+<p>
+Note: <a href="postconf.5.html#luser_relay">luser_relay</a> works only for the Postfix <a href="local.8.html">local(8)</a> delivery agent.
+</p>
+
+<p>
+Note: if you use this feature for accounts not in the UNIX password
+file, then you must specify "<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> =" (i.e. empty)
+in the <a href="postconf.5.html">main.cf</a> file, otherwise the Postfix SMTP server will reject mail
+for non-UNIX accounts with "User unknown in local recipient table".
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#luser_relay">luser_relay</a> = $user@other.host
+<a href="postconf.5.html#luser_relay">luser_relay</a> = $local@other.host
+<a href="postconf.5.html#luser_relay">luser_relay</a> = admin+$local
+</pre>
+
+
+</DD>
+
+<DT><b><a name="mail_name">mail_name</a>
+(default: Postfix)</b></DT><DD>
+
+<p>
+The mail system name that is displayed in Received: headers, in
+the SMTP greeting banner, and in bounced mail.
+</p>
+
+
+</DD>
+
+<DT><b><a name="mail_owner">mail_owner</a>
+(default: postfix)</b></DT><DD>
+
+<p>
+The UNIX system account that owns the Postfix queue and most Postfix
+daemon processes. Specify the name of an unprivileged user account
+that does not share a user or group ID with other accounts, and that
+owns no other files
+or processes on the system. In particular, don't specify nobody
+or daemon. PLEASE USE A DEDICATED USER ID AND GROUP ID.
+</p>
+
+<p>
+When this parameter value is changed you need to re-run "<b>postfix
+set-permissions</b>" (with Postfix version 2.0 and earlier:
+"<b>/etc/postfix/post-install set-permissions</b>".
+</p>
+
+
+</DD>
+
+<DT><b><a name="mail_release_date">mail_release_date</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The Postfix release date, in "YYYYMMDD" format.
+</p>
+
+
+</DD>
+
+<DT><b><a name="mail_spool_directory">mail_spool_directory</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The directory where <a href="local.8.html">local(8)</a> UNIX-style mailboxes are kept. The
+default setting depends on the system type. Specify a name ending
+in / for maildir-style delivery.
+</p>
+
+<p>
+Note: maildir delivery is done with the privileges of the recipient.
+If you use the <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a> setting for maildir style
+delivery, then you must create the top-level maildir directory in
+advance. Postfix will not create it.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a> = /var/mail
+<a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a> = /var/spool/mail
+</pre>
+
+
+</DD>
+
+<DT><b><a name="mail_version">mail_version</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The version of the mail system. Stable releases are named
+<i>major</i>.<i>minor</i>.<i>patchlevel</i>. Experimental releases
+also include the release date. The version string can be used in,
+for example, the SMTP greeting banner.
+</p>
+
+
+</DD>
+
+<DT><b><a name="mailbox_command">mailbox_command</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional external command that the <a href="local.8.html">local(8)</a> delivery agent should
+use for mailbox delivery. The command is run with the user ID and
+the primary group ID privileges of the recipient. Exception:
+command delivery for root executes with $<a href="postconf.5.html#default_privs">default_privs</a> privileges.
+This is not a problem, because 1) mail for root should always be
+aliased to a real user and 2) don't log in as root, use "su" instead.
+</p>
+
+<p>
+The following environment variables are exported to the command:
+</p>
+
+<dl>
+
+<dt><b>CLIENT_ADDRESS</b></dt>
+
+<dd>Remote client network address. Available in Postfix version 2.2 and
+later. </dd>
+
+<dt><b>CLIENT_HELO</b></dt>
+
+<dd>Remote client EHLO command parameter. Available in Postfix version 2.2
+and later.</dd>
+
+<dt><b>CLIENT_HOSTNAME</b></dt>
+
+<dd>Remote client hostname. Available in Postfix version 2.2 and later.
+</dd>
+
+<dt><b>CLIENT_PROTOCOL</b></dt>
+
+<dd>Remote client protocol. Available in Postfix version 2.2 and later.
+</dd>
+
+<dt><b>DOMAIN</b></dt>
+
+<dd>The domain part of the recipient address. </dd>
+
+<dt><b>EXTENSION</b></dt>
+
+<dd>The optional address extension. </dd>
+
+<dt><b>HOME</b></dt>
+
+<dd>The recipient home directory. </dd>
+
+<dt><b>LOCAL</b></dt>
+
+<dd>The recipient address localpart. </dd>
+
+<dt><b>LOGNAME</b></dt>
+
+<dd>The recipient's username. </dd>
+
+<dt><b>ORIGINAL_RECIPIENT</b></dt>
+
+<dd>The entire recipient address, before any address rewriting or
+aliasing. </dd>
+
+<dt><b>RECIPIENT</b></dt>
+
+<dd>The full recipient address. </dd>
+
+<dt><b>SASL_METHOD</b></dt>
+
+<dd>SASL authentication method specified in the remote client AUTH
+command. Available in Postfix version 2.2 and later. </dd>
+
+<dt><b>SASL_SENDER</b></dt>
+
+<dd>SASL sender address specified in the remote client MAIL FROM
+command. Available in Postfix version 2.2 and later. </dd>
+
+<dt><b>SASL_USER</b></dt>
+
+<dd>SASL username specified in the remote client AUTH command.
+Available in Postfix version 2.2 and later. </dd>
+
+<dt><b>SENDER</b></dt>
+
+<dd>The full sender address. </dd>
+
+<dt><b>SHELL</b></dt>
+
+<dd>The recipient's login shell. </dd>
+
+<dt><b>USER</b></dt>
+
+<dd>The recipient username. </dd>
+
+</dl>
+
+<p>
+Unlike other Postfix configuration parameters, the <a href="postconf.5.html#mailbox_command">mailbox_command</a>
+parameter is not subjected to $name substitutions. This is to make
+it easier to specify shell syntax (see example below).
+</p>
+
+<p>
+If you can, avoid shell meta characters because they will force
+Postfix to run an expensive shell process. If you're delivering
+via "procmail" then running a shell won't make a noticeable difference
+in the total cost.
+</p>
+
+<p>
+Note: if you use the <a href="postconf.5.html#mailbox_command">mailbox_command</a> feature to deliver mail
+system-wide, you must set up an alias that forwards mail for root
+to a real user.
+</p>
+
+<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
+is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
+<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
+<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. </p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#mailbox_command">mailbox_command</a> = /some/where/procmail
+<a href="postconf.5.html#mailbox_command">mailbox_command</a> = /some/where/procmail -a "$EXTENSION"
+<a href="postconf.5.html#mailbox_command">mailbox_command</a> = /some/where/maildrop -d "$USER"
+ -f "$SENDER" "$EXTENSION"
+</pre>
+
+
+</DD>
+
+<DT><b><a name="mailbox_command_maps">mailbox_command_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional lookup tables with per-recipient external commands to use
+for <a href="local.8.html">local(8)</a> mailbox delivery. Behavior is as with <a href="postconf.5.html#mailbox_command">mailbox_command</a>.
+</p>
+
+<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
+is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
+<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
+<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+
+</DD>
+
+<DT><b><a name="mailbox_delivery_lock">mailbox_delivery_lock</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+How to lock a UNIX-style <a href="local.8.html">local(8)</a> mailbox before attempting delivery.
+For a list of available file locking methods, use the "<b>postconf
+-l</b>" command.
+</p>
+
+<p>
+This setting is ignored with <b>maildir</b> style delivery,
+because such deliveries are safe without explicit locks.
+</p>
+
+<p>
+Note: The <b>dotlock</b> method requires that the recipient UID or
+GID has write access to the parent directory of the mailbox file.
+</p>
+
+<p>
+Note: the default setting of this parameter is system dependent.
+</p>
+
+
+</DD>
+
+<DT><b><a name="mailbox_size_limit">mailbox_size_limit</a>
+(default: 51200000)</b></DT><DD>
+
+<p> The maximal size of any <a href="local.8.html">local(8)</a> individual mailbox or maildir
+file, or zero (no limit). In fact, this limits the size of any
+file that is written to upon local delivery, including files written
+by external commands that are executed by the <a href="local.8.html">local(8)</a> delivery
+agent. </p>
+
+<p>
+This limit must not be smaller than the message size limit.
+</p>
+
+
+</DD>
+
+<DT><b><a name="mailbox_transport">mailbox_transport</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional message delivery transport that the <a href="local.8.html">local(8)</a> delivery
+agent should use for mailbox delivery to all local recipients,
+whether or not they are found in the UNIX passwd database.
+</p>
+
+<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
+is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
+<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
+<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. </p>
+
+
+</DD>
+
+<DT><b><a name="mailbox_transport_maps">mailbox_transport_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional lookup tables with per-recipient message delivery
+transports to use for <a href="local.8.html">local(8)</a> mailbox delivery, whether or not the
+recipients are found in the UNIX passwd database. </p>
+
+<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
+is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
+<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
+<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p> For safety reasons, this feature does not allow $number
+substitutions in regular expression maps. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="maillog_file">maillog_file</a>
+(default: empty)</b></DT><DD>
+
+<p> The name of an optional logfile that is written by the Postfix
+<a href="postlogd.8.html">postlogd(8)</a> service. An empty value selects logging to syslogd(8).
+Specify "/dev/stdout" to select logging to standard output. Stdout
+logging requires that Postfix is started with "postfix start-fg".
+</p>
+
+<p> Note 1: The <a href="postconf.5.html#maillog_file">maillog_file</a> parameter value must contain a prefix
+that is specified with the <a href="postconf.5.html#maillog_file_prefixes">maillog_file_prefixes</a> parameter. </p>
+
+<p> Note 2: Some Postfix non-daemon programs may still log information
+to syslogd(8), before they have processed their configuration
+parameters and command-line options. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="maillog_file_compressor">maillog_file_compressor</a>
+(default: gzip)</b></DT><DD>
+
+<p> The program to run after rotating $<a href="postconf.5.html#maillog_file">maillog_file</a> with "postfix
+logrotate". The command is run with the rotated logfile name as its
+first argument. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="maillog_file_prefixes">maillog_file_prefixes</a>
+(default: /var, /dev/stdout)</b></DT><DD>
+
+<p> A list of allowed prefixes for a <a href="postconf.5.html#maillog_file">maillog_file</a> value. This is a
+safety feature to contain the damage from a single configuration
+mistake. Specify one or more prefix strings, separated by comma or
+whitespace. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="maillog_file_rotate_suffix">maillog_file_rotate_suffix</a>
+(default: %Y%m%d-%H%M%S)</b></DT><DD>
+
+<p> The format of the suffix to append to $<a href="postconf.5.html#maillog_file">maillog_file</a> while rotating
+the file with "postfix logrotate". See strftime(3) for syntax. The
+default suffix, YYYYMMDD-HHMMSS, allows logs to be rotated frequently.
+</p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="mailq_path">mailq_path</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+Sendmail compatibility feature that specifies where the Postfix
+<a href="mailq.1.html">mailq(1)</a> command is installed. This command can be used to
+list the Postfix mail queue.
+</p>
+
+
+</DD>
+
+<DT><b><a name="manpage_directory">manpage_directory</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+Where the Postfix manual pages are installed.
+</p>
+
+
+</DD>
+
+<DT><b><a name="maps_rbl_domains">maps_rbl_domains</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Obsolete feature: use the <a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a> feature instead.
+</p>
+
+
+</DD>
+
+<DT><b><a name="maps_rbl_reject_code">maps_rbl_reject_code</a>
+(default: 554)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code when a remote SMTP
+client request is blocked by the <a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a>, <a href="postconf.5.html#reject_rhsbl_client">reject_rhsbl_client</a>,
+<a href="postconf.5.html#reject_rhsbl_reverse_client">reject_rhsbl_reverse_client</a>, <a href="postconf.5.html#reject_rhsbl_sender">reject_rhsbl_sender</a> or
+<a href="postconf.5.html#reject_rhsbl_recipient">reject_rhsbl_recipient</a> restriction.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="masquerade_classes">masquerade_classes</a>
+(default: envelope_sender, header_sender, header_recipient)</b></DT><DD>
+
+<p>
+What addresses are subject to address masquerading.
+</p>
+
+<p>
+By default, address masquerading is limited to envelope sender
+addresses, and to header sender and header recipient addresses.
+This allows you to use address masquerading on a mail gateway while
+still being able to forward mail to users on individual machines.
+</p>
+
+<p>
+Specify zero or more of: envelope_sender, envelope_recipient,
+header_sender, header_recipient
+</p>
+
+
+</DD>
+
+<DT><b><a name="masquerade_domains">masquerade_domains</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional list of domains whose subdomain structure will be stripped
+off in email addresses.
+</p>
+
+<p>
+The list is processed left to right, and processing stops at the
+first match. Thus,
+</p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#masquerade_domains">masquerade_domains</a> = foo.example.com example.com
+</pre>
+</blockquote>
+
+<p>
+strips "user@any.thing.foo.example.com" to "user@foo.example.com",
+but strips "user@any.thing.else.example.com" to "user@example.com".
+</p>
+
+<p>
+A domain name prefixed with ! means do not masquerade this domain
+or its subdomains. Thus,
+</p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#masquerade_domains">masquerade_domains</a> = !foo.example.com example.com
+</pre>
+</blockquote>
+
+<p>
+does not change "user@any.thing.foo.example.com" or "user@foo.example.com",
+but strips "user@any.thing.else.example.com" to "user@example.com".
+</p>
+
+<p> Note: with Postfix version 2.2, message header address masquerading
+happens only when message header address rewriting is enabled: </p>
+
+<ul>
+
+<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,
+
+<li> The message is received from a network client that matches
+$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,
+
+<li> The message is received from the network, and the
+<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.
+
+</ul>
+
+<p> To get the behavior before Postfix version 2.2, specify
+"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all". </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#masquerade_domains">masquerade_domains</a> = $<a href="postconf.5.html#mydomain">mydomain</a>
+</pre>
+
+
+</DD>
+
+<DT><b><a name="masquerade_exceptions">masquerade_exceptions</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional list of user names that are not subjected to address
+masquerading, even when their addresses match $<a href="postconf.5.html#masquerade_domains">masquerade_domains</a>.
+</p>
+
+<p>
+By default, address masquerading makes no exceptions.
+</p>
+
+<p>
+Specify a list of user names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns,
+separated by commas and/or whitespace. The list is matched left to
+right, and the search stops on the first match. A "/file/name"
+pattern is replaced
+by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name
+matches a lookup key (the lookup result is ignored). Continue long
+lines by starting the next line with whitespace. Specify "!pattern"
+to exclude a name from the list. The form "!/file/name" is supported
+only in Postfix version 2.4 and later. </p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#masquerade_exceptions">masquerade_exceptions</a> = root, mailer-daemon
+<a href="postconf.5.html#masquerade_exceptions">masquerade_exceptions</a> = root
+</pre>
+
+
+</DD>
+
+<DT><b><a name="master_service_disable">master_service_disable</a>
+(default: empty)</b></DT><DD>
+
+<p> Selectively disable <a href="master.8.html">master(8)</a> listener ports by service type
+or by service name and type. Specify a list of service types
+("inet", "unix", "fifo", or "pass") or "name/type" tuples, where
+"name" is the first field of a <a href="master.5.html">master.cf</a> entry and "type" is a
+service type. As with other Postfix matchlists, a search stops at
+the first match. Specify "!pattern" to exclude a service from the
+list. By default, all <a href="master.8.html">master(8)</a> listener ports are enabled. </p>
+
+<p> Note: this feature does not support "/file/name" or "<a href="DATABASE_README.html">type:table</a>"
+patterns, nor does it support wildcards such as "*" or "all". This
+is intentional. </p>
+
+<p> Examples: </p>
+
+<pre>
+# With Postfix 2.6..2.10 use '.' instead of '/'.
+# Turn on all <a href="master.8.html">master(8)</a> listener ports (the default).
+<a href="postconf.5.html#master_service_disable">master_service_disable</a> =
+# Turn off only the main SMTP listener port.
+<a href="postconf.5.html#master_service_disable">master_service_disable</a> = smtp/inet
+# Turn off all TCP/IP listener ports.
+<a href="postconf.5.html#master_service_disable">master_service_disable</a> = inet
+# Turn off all TCP/IP listener ports except "foo".
+<a href="postconf.5.html#master_service_disable">master_service_disable</a> = !foo/inet, inet
+</pre>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="max_idle">max_idle</a>
+(default: 100s)</b></DT><DD>
+
+<p>
+The maximum amount of time that an idle Postfix daemon process waits
+for an incoming connection before terminating voluntarily. This
+parameter
+is ignored by the Postfix queue manager and by other long-lived
+Postfix daemon processes.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="max_use">max_use</a>
+(default: 100)</b></DT><DD>
+
+<p>
+The maximal number of incoming connections that a Postfix daemon
+process will service before terminating voluntarily. This parameter
+is ignored by the Postfix queue
+manager and by other long-lived Postfix daemon processes.
+</p>
+
+
+</DD>
+
+<DT><b><a name="maximal_backoff_time">maximal_backoff_time</a>
+(default: 4000s)</b></DT><DD>
+
+<p>
+The maximal time between attempts to deliver a deferred message.
+</p>
+
+<p> This parameter should be set to a value greater than or equal
+to $<a href="postconf.5.html#minimal_backoff_time">minimal_backoff_time</a>. See also $<a href="postconf.5.html#queue_run_delay">queue_run_delay</a>. </p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="maximal_queue_lifetime">maximal_queue_lifetime</a>
+(default: 5d)</b></DT><DD>
+
+<p>
+Consider a message as undeliverable, when delivery fails with a
+temporary error, and the time in the queue has reached the
+<a href="postconf.5.html#maximal_queue_lifetime">maximal_queue_lifetime</a> limit.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is d (days).
+</p>
+
+<p>
+Specify 0 when mail delivery should be tried only once.
+</p>
+
+
+</DD>
+
+<DT><b><a name="message_drop_headers">message_drop_headers</a>
+(default: bcc, content-length, resent-bcc, return-path)</b></DT><DD>
+
+<p> Names of message headers that the <a href="cleanup.8.html">cleanup(8)</a> daemon will remove
+after applying <a href="header_checks.5.html">header_checks(5)</a> and before invoking Milter applications.
+The default setting is compatible with Postfix &lt; 3.0. </p>
+
+<p> Specify a list of header names, separated by comma or space.
+Names are matched in a case-insensitive manner. The list of supported
+header names is limited only by available memory. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="message_reject_characters">message_reject_characters</a>
+(default: empty)</b></DT><DD>
+
+<p> The set of characters that Postfix will reject in message
+content. The usual C-like escape sequences are recognized: <tt>\a
+\b \f \n \r \t \v \<i>ddd</i></tt> (up to three octal digits) and
+<tt>\\</tt>. </p>
+
+<p> Note 1: this feature does not recognize text that requires MIME
+decoding. It inspects raw message content, just like <a href="postconf.5.html#header_checks">header_checks</a>
+and <a href="postconf.5.html#body_checks">body_checks</a>. </p>
+
+<p> Note 2: this feature is disabled with "<a href="postconf.5.html#receive_override_options">receive_override_options</a>
+= <a href="postconf.5.html#no_header_body_checks">no_header_body_checks</a>". </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#message_reject_characters">message_reject_characters</a> = \0
+</pre>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="message_size_limit">message_size_limit</a>
+(default: 10240000)</b></DT><DD>
+
+<p>
+The maximal size in bytes of a message, including envelope information.
+</p>
+
+<p> Note: be careful when making changes. Excessively small values
+will result in the loss of non-delivery notifications, when a bounce
+message size exceeds the local or remote MTA's message size limit.
+</p>
+
+
+</DD>
+
+<DT><b><a name="message_strip_characters">message_strip_characters</a>
+(default: empty)</b></DT><DD>
+
+<p> The set of characters that Postfix will remove from message
+content. The usual C-like escape sequences are recognized: <tt>\a
+\b \f \n \r \t \v \<i>ddd</i></tt> (up to three octal digits) and
+<tt>\\</tt>. </p>
+
+<p> Note 1: this feature does not recognize text that requires MIME
+decoding. It inspects raw message content, just like <a href="postconf.5.html#header_checks">header_checks</a>
+and <a href="postconf.5.html#body_checks">body_checks</a>. </p>
+
+<p> Note 2: this feature is disabled with "<a href="postconf.5.html#receive_override_options">receive_override_options</a>
+= <a href="postconf.5.html#no_header_body_checks">no_header_body_checks</a>". </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#message_strip_characters">message_strip_characters</a> = \0
+</pre>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="meta_directory">meta_directory</a>
+(default: see 'postconf -d' output)</b></DT><DD>
+
+<p> The location of non-executable files that are shared among
+multiple Postfix instances, such as postfix-files, dynamicmaps.cf,
+and the multi-instance template files <a href="postconf.5.html">main.cf</a>.proto and <a href="master.5.html">master.cf</a>.proto.
+This directory should contain only Postfix-related files. Typically,
+the <a href="postconf.5.html#meta_directory">meta_directory</a> parameter has the same default as the <a href="postconf.5.html#config_directory">config_directory</a>
+parameter (/etc/postfix or /usr/local/etc/postfix). </p>
+
+<p> For backwards compatibility with Postfix versions 2.6..2.11,
+specify "<a href="postconf.5.html#meta_directory">meta_directory</a> = $<a href="postconf.5.html#daemon_directory">daemon_directory</a>" in <a href="postconf.5.html">main.cf</a> before
+installing or upgrading Postfix, or specify "<a href="postconf.5.html#meta_directory">meta_directory</a> =
+/path/name" on the "make makefiles", "make install" or "make upgrade"
+command line. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_command_timeout">milter_command_timeout</a>
+(default: 30s)</b></DT><DD>
+
+<p> The time limit for sending an SMTP command to a Milter (mail
+filter) application, and for receiving the response. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). </p>
+
+<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
+(weeks). The default time unit is s (seconds). </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_connect_macros">milter_connect_macros</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The macros that are sent to Milter (mail filter) applications
+after completion of an SMTP connection. See <a href="MILTER_README.html">MILTER_README</a>
+for a list of available macro names and their meanings. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_connect_timeout">milter_connect_timeout</a>
+(default: 30s)</b></DT><DD>
+
+<p> The time limit for connecting to a Milter (mail filter)
+application, and for negotiating protocol options. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). </p>
+
+<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
+(weeks). The default time unit is s (seconds). </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_content_timeout">milter_content_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p> The time limit for sending message content to a Milter (mail
+filter) application, and for receiving the response. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). </p>
+
+<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
+(weeks). The default time unit is s (seconds). </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_data_macros">milter_data_macros</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The macros that are sent to version 4 or higher Milter (mail
+filter) applications after the SMTP DATA command. See <a href="MILTER_README.html">MILTER_README</a>
+for a list of available macro names and their meanings. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_default_action">milter_default_action</a>
+(default: tempfail)</b></DT><DD>
+
+<p> The default action when a Milter (mail filter) application is
+unavailable or mis-configured. Specify one of the following: </p>
+
+<dl compact>
+
+<dt>accept</dt> <dd>Proceed as if the mail filter was not present.
+</dd>
+
+<dt>reject</dt> <dd>Reject all further commands in this session
+with a permanent status code.</dd>
+
+<dt>tempfail</dt> <dd>Reject all further commands in this session
+with a temporary status code. </dd>
+
+<dt>quarantine</dt> <dd>Like "accept", but freeze the message in
+the "<a href="QSHAPE_README.html#hold_queue">hold" queue</a>. Available with Postfix 2.6 and later. </dd>
+
+</dl>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_end_of_data_macros">milter_end_of_data_macros</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The macros that are sent to Milter (mail filter) applications
+after the message end-of-data. See <a href="MILTER_README.html">MILTER_README</a> for a list of
+available macro names and their meanings. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_end_of_header_macros">milter_end_of_header_macros</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The macros that are sent to Milter (mail filter) applications
+after the end of the message header. See <a href="MILTER_README.html">MILTER_README</a> for a list
+of available macro names and their meanings. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_header_checks">milter_header_checks</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional lookup tables for content inspection of message headers
+that are produced by Milter applications. See the <a href="header_checks.5.html">header_checks(5)</a>
+manual page available actions. Currently, PREPEND is not implemented.
+</p>
+
+<p> The following example sends all mail that is marked as SPAM to
+a spam handling machine. Note that matches are case-insensitive
+by default. </p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#milter_header_checks">milter_header_checks</a> = <a href="pcre_table.5.html">pcre</a>:/etc/postfix/<a href="postconf.5.html#milter_header_checks">milter_header_checks</a>
+</pre>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html#milter_header_checks">milter_header_checks</a>:
+ /^X-SPAM-FLAG:\s+YES/ FILTER mysmtp:sanitizer.example.com:25
+</pre>
+
+<p> The <a href="postconf.5.html#milter_header_checks">milter_header_checks</a> mechanism could also be used for
+whitelisting. For example it could be used to skip heavy content
+inspection for DKIM-signed mail from known friendly domains. </p>
+
+<p> This feature is available in Postfix 2.7, and as an optional
+patch for Postfix 2.6. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_helo_macros">milter_helo_macros</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The macros that are sent to Milter (mail filter) applications
+after the SMTP HELO or EHLO command. See
+<a href="MILTER_README.html">MILTER_README</a> for a list of available macro names and their meanings.
+</p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_macro_daemon_name">milter_macro_daemon_name</a>
+(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</b></DT><DD>
+
+<p> The {daemon_name} macro value for Milter (mail filter) applications.
+See <a href="MILTER_README.html">MILTER_README</a> for a list of available macro names and their
+meanings. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_macro_defaults">milter_macro_defaults</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional list of <i>name=value</i> pairs that specify default
+values for arbitrary macros that Postfix may send to Milter
+applications. These defaults are used when there is no corresponding
+information from the message delivery context. </p>
+
+<p> Specify <i>name=value</i> or <i>{name}=value</i> pairs separated
+by comma or whitespace. Enclose a pair in "{}" when a value contains
+comma or whitespace (this form ignores whitespace after the enclosing
+"{", around the "=", and before the enclosing "}"). </p>
+
+<p> This feature is available in Postfix 3.1 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_macro_v">milter_macro_v</a>
+(default: $<a href="postconf.5.html#mail_name">mail_name</a> $<a href="postconf.5.html#mail_version">mail_version</a>)</b></DT><DD>
+
+<p> The {v} macro value for Milter (mail filter) applications.
+See <a href="MILTER_README.html">MILTER_README</a> for a list of available macro names and their
+meanings. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_mail_macros">milter_mail_macros</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The macros that are sent to Milter (mail filter) applications
+after the SMTP MAIL FROM command. See <a href="MILTER_README.html">MILTER_README</a>
+for a list of available macro names and their meanings. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_protocol">milter_protocol</a>
+(default: 6)</b></DT><DD>
+
+<p> The mail filter protocol version and optional protocol extensions
+for communication with a Milter application; prior to Postfix 2.6
+the default protocol is 2. Postfix
+sends this version number during the initial protocol handshake.
+It should match the version number that is expected by the mail
+filter application (or by its Milter library). </p>
+
+<p>Protocol versions: </p>
+
+<dl compact>
+
+<dt>2</dt> <dd>Use Sendmail 8 mail filter protocol version 2 (default
+with Sendmail version 8.11 .. 8.13 and Postfix version 2.3 ..
+2.5).</dd>
+
+<dt>3</dt> <dd>Use Sendmail 8 mail filter protocol version 3.</dd>
+
+<dt>4</dt> <dd>Use Sendmail 8 mail filter protocol version 4.</dd>
+
+<dt>6</dt> <dd>Use Sendmail 8 mail filter protocol version 6 (default
+with Sendmail version 8.14 and Postfix version 2.6).</dd>
+
+</dl>
+
+<p>Protocol extensions: </p>
+
+<dl compact>
+
+<dt>no_header_reply</dt> <dd> Specify this when the Milter application
+will not reply for each individual message header.</dd>
+
+</dl>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_rcpt_macros">milter_rcpt_macros</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The macros that are sent to Milter (mail filter) applications
+after the SMTP RCPT TO command. See <a href="MILTER_README.html">MILTER_README</a>
+for a list of available macro names and their meanings. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="milter_unknown_command_macros">milter_unknown_command_macros</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The macros that are sent to version 3 or higher Milter (mail
+filter) applications after an unknown SMTP command. See <a href="MILTER_README.html">MILTER_README</a>
+for a list of available macro names and their meanings. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="mime_boundary_length_limit">mime_boundary_length_limit</a>
+(default: 2048)</b></DT><DD>
+
+<p>
+The maximal length of MIME multipart boundary strings. The MIME
+processor is unable to distinguish between boundary strings that
+do not differ in the first $<a href="postconf.5.html#mime_boundary_length_limit">mime_boundary_length_limit</a> characters.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="mime_header_checks">mime_header_checks</a>
+(default: $<a href="postconf.5.html#header_checks">header_checks</a>)</b></DT><DD>
+
+<p>
+Optional lookup tables for content inspection of MIME related
+message headers, as described in the <a href="header_checks.5.html">header_checks(5)</a> manual page.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="mime_nesting_limit">mime_nesting_limit</a>
+(default: 100)</b></DT><DD>
+
+<p>
+The maximal recursion level that the MIME processor will handle.
+Postfix refuses mail that is nested deeper than the specified limit.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="minimal_backoff_time">minimal_backoff_time</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The minimal time between attempts to deliver a deferred message;
+prior to Postfix 2.4 the default value was 1000s.
+</p>
+
+<p>
+This parameter also limits the time an unreachable destination is
+kept in the short-term, in-memory, destination status cache.
+</p>
+
+<p> This parameter should be set greater than or equal to
+$<a href="postconf.5.html#queue_run_delay">queue_run_delay</a>. See also $<a href="postconf.5.html#maximal_backoff_time">maximal_backoff_time</a>. </p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="multi_instance_directories">multi_instance_directories</a>
+(default: empty)</b></DT><DD>
+
+<p> An optional list of non-default Postfix configuration directories;
+these directories belong to additional Postfix instances that share
+the Postfix executable files and documentation with the default
+Postfix instance, and that are started, stopped, etc., together
+with the default Postfix instance. Specify a list of pathnames
+separated by comma or whitespace. </p>
+
+<p> When $<a href="postconf.5.html#multi_instance_directories">multi_instance_directories</a> is empty, the <a href="postfix.1.html">postfix(1)</a> command
+runs in single-instance mode and operates on a single Postfix
+instance only. Otherwise, the <a href="postfix.1.html">postfix(1)</a> command runs in multi-instance
+mode and invokes the multi-instance manager specified with the
+<a href="postconf.5.html#multi_instance_wrapper">multi_instance_wrapper</a> parameter. The multi-instance manager in
+turn executes <a href="postfix.1.html">postfix(1)</a> commands for the default instance and for
+all Postfix instances in $<a href="postconf.5.html#multi_instance_directories">multi_instance_directories</a>. </p>
+
+<p> Currently, this parameter setting is ignored except for the
+default <a href="postconf.5.html">main.cf</a> file. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="multi_instance_enable">multi_instance_enable</a>
+(default: no)</b></DT><DD>
+
+<p> Allow this Postfix instance to be started, stopped, etc., by a
+multi-instance manager. By default, new instances are created in
+a safe state that prevents them from being started inadvertently.
+This parameter is reserved for the multi-instance manager. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="multi_instance_group">multi_instance_group</a>
+(default: empty)</b></DT><DD>
+
+<p> The optional instance group name of this Postfix instance. A
+group identifies closely-related Postfix instances that the
+multi-instance manager can start, stop, etc., as a unit. This
+parameter is reserved for the multi-instance manager. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="multi_instance_name">multi_instance_name</a>
+(default: empty)</b></DT><DD>
+
+<p> The optional instance name of this Postfix instance. This name
+becomes also the default value for the <a href="postconf.5.html#syslog_name">syslog_name</a> parameter. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="multi_instance_wrapper">multi_instance_wrapper</a>
+(default: empty)</b></DT><DD>
+
+<p> The pathname of a multi-instance manager command that the
+<a href="postfix.1.html">postfix(1)</a> command invokes when the <a href="postconf.5.html#multi_instance_directories">multi_instance_directories</a>
+parameter value is non-empty. The pathname may be followed by
+initial command arguments separated by whitespace; shell
+metacharacters such as quotes are not supported in this context.
+</p>
+
+<p> The <a href="postfix.1.html">postfix(1)</a> command invokes the manager command with the
+<a href="postfix.1.html">postfix(1)</a> non-option command arguments on the manager command line,
+and with all installation configuration parameters exported into
+the manager command process environment. The manager command in
+turn invokes the <a href="postfix.1.html">postfix(1)</a> command for individual Postfix instances
+as "postfix -c <i><a href="postconf.5.html#config_directory">config_directory</a></i> <i>command</i>". </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="multi_recipient_bounce_reject_code">multi_recipient_bounce_reject_code</a>
+(default: 550)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code when a remote SMTP
+client request is blocked by the <a href="postconf.5.html#reject_multi_recipient_bounce">reject_multi_recipient_bounce</a>
+restriction.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="mydestination">mydestination</a>
+(default: $<a href="postconf.5.html#myhostname">myhostname</a>, localhost.$<a href="postconf.5.html#mydomain">mydomain</a>, localhost)</b></DT><DD>
+
+<p> The list of domains that are delivered via the $<a href="postconf.5.html#local_transport">local_transport</a>
+mail delivery transport. By default this is the Postfix <a href="local.8.html">local(8)</a>
+delivery agent which looks up all recipients in /etc/passwd and
+/etc/aliases. The SMTP server validates recipient addresses with
+$<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> and rejects non-existent recipients. See also
+the <a href="ADDRESS_CLASS_README.html#local_domain_class">local domain</a> class in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> file.
+</p>
+
+<p>
+The default <a href="postconf.5.html#mydestination">mydestination</a> value specifies names for the local
+machine only. On a mail domain gateway, you should also include
+$<a href="postconf.5.html#mydomain">mydomain</a>.
+</p>
+
+<p>
+The $<a href="postconf.5.html#local_transport">local_transport</a> delivery method is also selected for mail
+addressed to user@[the.net.work.address] of the mail system (the
+IP addresses specified with the <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> and <a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>
+parameters).
+</p>
+
+<p>
+Warnings:
+</p>
+
+<ul>
+
+<li><p>Do not specify the names of virtual domains - those domains
+are specified elsewhere. See <a href="VIRTUAL_README.html">VIRTUAL_README</a> for more information. </p>
+
+<li><p>Do not specify the names of domains that this machine is
+backup MX host for. See <a href="STANDARD_CONFIGURATION_README.html">STANDARD_CONFIGURATION_README</a> for how to
+set up backup MX hosts. </p>
+
+<li><p>By default, the Postfix SMTP server rejects mail for recipients
+not listed with the <a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> parameter. See the
+<a href="postconf.5.html">postconf(5)</a> manual for a description of the <a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a>
+and <a href="postconf.5.html#unknown_local_recipient_reject_code">unknown_local_recipient_reject_code</a> parameters. </p>
+
+</ul>
+
+<p>
+Specify a list of host or domain names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>"
+patterns, separated by commas and/or whitespace. A "/file/name"
+pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table
+is matched when a name matches a lookup key (the lookup result is
+ignored). Continue long lines by starting the next line with
+whitespace. </p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#mydestination">mydestination</a> = $<a href="postconf.5.html#myhostname">myhostname</a>, localhost.$<a href="postconf.5.html#mydomain">mydomain</a> $<a href="postconf.5.html#mydomain">mydomain</a>
+<a href="postconf.5.html#mydestination">mydestination</a> = $<a href="postconf.5.html#myhostname">myhostname</a>, localhost.$<a href="postconf.5.html#mydomain">mydomain</a> www.$<a href="postconf.5.html#mydomain">mydomain</a>, ftp.$<a href="postconf.5.html#mydomain">mydomain</a>
+</pre>
+
+
+</DD>
+
+<DT><b><a name="mydomain">mydomain</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The internet domain name of this mail system. The default is to
+use $<a href="postconf.5.html#myhostname">myhostname</a> minus the first component, or "localdomain" (Postfix
+2.3 and later). $<a href="postconf.5.html#mydomain">mydomain</a> is used as
+a default value for many other configuration parameters.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#mydomain">mydomain</a> = domain.tld
+</pre>
+
+
+</DD>
+
+<DT><b><a name="myhostname">myhostname</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The internet hostname of this mail system. The default is to use
+the fully-qualified domain name (FQDN) from gethostname(), or to
+use the non-FQDN result from gethostname() and append ".$<a href="postconf.5.html#mydomain">mydomain</a>".
+$<a href="postconf.5.html#myhostname">myhostname</a> is used as a default value for many other configuration
+parameters. </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#myhostname">myhostname</a> = host.example.com
+</pre>
+
+
+</DD>
+
+<DT><b><a name="mynetworks">mynetworks</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The list of "trusted" remote SMTP clients that have more privileges than
+"strangers".
+</p>
+
+<p>
+In particular, "trusted" SMTP clients are allowed to relay mail
+through Postfix. See the <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a> parameter
+description in the <a href="postconf.5.html">postconf(5)</a> manual.
+</p>
+
+<p>
+You can specify the list of "trusted" network addresses by hand
+or you can let Postfix do it for you (which is the default).
+See the description of the <a href="postconf.5.html#mynetworks_style">mynetworks_style</a> parameter for more
+information.
+</p>
+
+<p>
+If you specify the <a href="postconf.5.html#mynetworks">mynetworks</a> list by hand,
+Postfix ignores the <a href="postconf.5.html#mynetworks_style">mynetworks_style</a> setting.
+</p>
+
+<p> Specify a list of network addresses or network/netmask patterns,
+separated by commas and/or whitespace. Continue long lines by
+starting the next line with whitespace. </p>
+
+<p> The netmask specifies the number of bits in the network part
+of a host address. You can also specify "/file/name" or "<a href="DATABASE_README.html">type:table</a>"
+patterns. A "/file/name" pattern is replaced by its contents; a
+"<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a table entry matches a
+lookup string (the lookup result is ignored). </p>
+
+<p> The list is matched left to right, and the search stops on the
+first match. Specify "!pattern" to exclude an address or network
+block from the list. The form "!/file/name" is supported only
+in Postfix version 2.4 and later. </p>
+
+<p> Note 1: Pattern matching of domain names is controlled by the
+or absence of "<a href="postconf.5.html#mynetworks">mynetworks</a>" in the <a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a>
+parameter value. </p>
+
+<p> Note 2: IP version 6 address information must be specified inside
+<tt>[]</tt> in the <a href="postconf.5.html#mynetworks">mynetworks</a> value, and in files specified with
+"/file/name". IP version 6 addresses contain the ":" character,
+and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>" pattern. </p>
+
+<p> Examples: </p>
+
+<pre>
+<a href="postconf.5.html#mynetworks">mynetworks</a> = 127.0.0.0/8 168.100.189.0/28
+<a href="postconf.5.html#mynetworks">mynetworks</a> = !192.168.0.1, 192.168.0.0/28
+<a href="postconf.5.html#mynetworks">mynetworks</a> = 127.0.0.0/8 168.100.189.0/28 [::1]/128 [2001:240:587::]/64
+<a href="postconf.5.html#mynetworks">mynetworks</a> = $<a href="postconf.5.html#config_directory">config_directory</a>/mynetworks
+<a href="postconf.5.html#mynetworks">mynetworks</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/network_table
+</pre>
+
+
+</DD>
+
+<DT><b><a name="mynetworks_style">mynetworks_style</a>
+(default: Postfix &ge; 3.0: host, Postfix &lt; 3.0: subnet)</b></DT><DD>
+
+<p>
+The method to generate the default value for the <a href="postconf.5.html#mynetworks">mynetworks</a> parameter.
+This is the list of trusted networks for relay access control etc.
+</p>
+
+<ul>
+
+<li><p>Specify "<a href="postconf.5.html#mynetworks_style">mynetworks_style</a> = host" when Postfix should
+"trust" only the local machine. </p>
+
+<li><p>Specify "<a href="postconf.5.html#mynetworks_style">mynetworks_style</a> = subnet" when Postfix
+should "trust" remote SMTP clients in the same IP subnetworks as the local
+machine. On Linux, this works correctly only with interfaces
+specified with the "ifconfig" command. </p>
+
+<li><p>Specify "<a href="postconf.5.html#mynetworks_style">mynetworks_style</a> = class" when Postfix should
+"trust" remote SMTP clients in the same IP class A/B/C networks as the
+local machine. Caution: this may cause
+Postfix to "trust" your entire provider's network. Instead, specify
+an explicit <a href="postconf.5.html#mynetworks">mynetworks</a> list by hand, as described with the <a href="postconf.5.html#mynetworks">mynetworks</a>
+configuration parameter. </p>
+
+</ul>
+
+
+</DD>
+
+<DT><b><a name="myorigin">myorigin</a>
+(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</b></DT><DD>
+
+<p>
+The domain name that locally-posted mail appears to come
+from, and that locally posted mail is delivered to. The default,
+$<a href="postconf.5.html#myhostname">myhostname</a>, is adequate for small sites. If you run a domain with
+multiple machines, you should (1) change this to $<a href="postconf.5.html#mydomain">mydomain</a> and (2)
+set up a domain-wide alias database that aliases each user to
+user@that.users.mailhost.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#myorigin">myorigin</a> = $<a href="postconf.5.html#mydomain">mydomain</a>
+</pre>
+
+
+</DD>
+
+<DT><b><a name="nested_header_checks">nested_header_checks</a>
+(default: $<a href="postconf.5.html#header_checks">header_checks</a>)</b></DT><DD>
+
+<p>
+Optional lookup tables for content inspection of non-MIME message
+headers in attached messages, as described in the <a href="header_checks.5.html">header_checks(5)</a>
+manual page.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="newaliases_path">newaliases_path</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+Sendmail compatibility feature that specifies the location of the
+<a href="newaliases.1.html">newaliases(1)</a> command. This command can be used to rebuild the
+<a href="local.8.html">local(8)</a> <a href="aliases.5.html">aliases(5)</a> database.
+</p>
+
+
+</DD>
+
+<DT><b><a name="non_fqdn_reject_code">non_fqdn_reject_code</a>
+(default: 504)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server reply code when a client request
+is rejected by the <a href="postconf.5.html#reject_non_fqdn_helo_hostname">reject_non_fqdn_helo_hostname</a>, <a href="postconf.5.html#reject_non_fqdn_sender">reject_non_fqdn_sender</a>
+or <a href="postconf.5.html#reject_non_fqdn_recipient">reject_non_fqdn_recipient</a> restriction.
+</p>
+
+
+</DD>
+
+<DT><b><a name="non_smtpd_milters">non_smtpd_milters</a>
+(default: empty)</b></DT><DD>
+
+<p> A list of Milter (mail filter) applications for new mail that
+does not arrive via the Postfix <a href="smtpd.8.html">smtpd(8)</a> server. This includes local
+submission via the <a href="sendmail.1.html">sendmail(1)</a> command line, new mail that arrives
+via the Postfix <a href="qmqpd.8.html">qmqpd(8)</a> server, and old mail that is re-injected
+into the queue with "postsuper -r". Specify space or comma as
+separator. See the <a href="MILTER_README.html">MILTER_README</a> document for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="notify_classes">notify_classes</a>
+(default: resource, software)</b></DT><DD>
+
+<p>
+The list of error classes that are reported to the postmaster. The
+default is to report only the most serious problems. The paranoid
+may wish to turn on the policy (UCE and mail relaying) and protocol
+error (broken mail software) reports.
+</p>
+
+<p> NOTE: postmaster notifications may contain confidential information
+such as SASL passwords or message content. It is the system
+administrator's responsibility to treat such information with care.
+</p>
+
+<p>
+The error classes are:
+</p>
+
+<dl>
+
+<dt><b>bounce</b> (also implies <b>2bounce</b>)</dt>
+
+<dd>Send the postmaster copies of the headers of bounced mail, and
+send transcripts of SMTP sessions when Postfix rejects mail. The
+notification is sent to the address specified with the
+<a href="postconf.5.html#bounce_notice_recipient">bounce_notice_recipient</a> configuration parameter (default: postmaster).
+</dd>
+
+<dt><b>2bounce</b></dt>
+
+<dd>Send undeliverable bounced mail to the postmaster. The notification
+is sent to the address specified with the <a href="postconf.5.html#2bounce_notice_recipient">2bounce_notice_recipient</a>
+configuration parameter (default: postmaster). </dd>
+
+<dt><b>data</b></dt>
+
+<dd>Send the postmaster a transcript of the SMTP session with an
+error because a critical data file was unavailable. The notification
+is sent to the address specified with the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a>
+configuration parameter (default: postmaster). <br> This feature
+is available in Postfix 2.9 and later. </dd>
+
+<dt><b>delay</b></dt>
+
+<dd>Send the postmaster copies of the headers of delayed mail (see
+<a href="postconf.5.html#delay_warning_time">delay_warning_time</a>). The
+notification is sent to the address specified with the
+<a href="postconf.5.html#delay_notice_recipient">delay_notice_recipient</a> configuration parameter (default: postmaster).
+</dd>
+
+<dt><b>policy</b></dt>
+
+<dd>Send the postmaster a transcript of the SMTP session when a
+client request was rejected because of (UCE) policy. The notification
+is sent to the address specified with the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a>
+configuration parameter (default: postmaster). </dd>
+
+<dt><b>protocol</b></dt>
+
+<dd>Send the postmaster a transcript of the SMTP session in case
+of client or server protocol errors. The notification is sent to
+the address specified with the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a> configuration
+parameter (default: postmaster). </dd>
+
+<dt><b>resource</b></dt>
+
+<dd>Inform the postmaster of mail not delivered due to resource
+problems. The notification is sent to the address specified with
+the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a> configuration parameter (default:
+postmaster). </dd>
+
+<dt><b>software</b></dt>
+
+<dd>Inform the postmaster of mail not delivered due to software
+problems. The notification is sent to the address specified with
+the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a> configuration parameter (default:
+postmaster). </dd>
+
+</dl>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#notify_classes">notify_classes</a> = bounce, delay, policy, protocol, resource, software
+<a href="postconf.5.html#notify_classes">notify_classes</a> = 2bounce, resource, software
+</pre>
+
+
+</DD>
+
+<DT><b><a name="nullmx_reject_code">nullmx_reject_code</a>
+(default: 556)</b></DT><DD>
+
+<p> The numerical reply code when the Postfix SMTP server rejects
+a sender or recipient address because its domain has a nullmx DNS
+record (an MX record with an empty hostname). This is one of the
+possible replies from the restrictions <a href="postconf.5.html#reject_unknown_sender_domain">reject_unknown_sender_domain</a>
+and <a href="postconf.5.html#reject_unknown_recipient_domain">reject_unknown_recipient_domain</a>. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="openssl_path">openssl_path</a>
+(default: openssl)</b></DT><DD>
+
+<p>
+The location of the OpenSSL command line program openssl(1). This
+is used by the "<b><a href="postfix-tls.1.html">postfix tls</a></b>" command to create private keys,
+certificate signing requests, self-signed certificates, and to
+compute public key digests for DANE TLSA records. In multi-instance
+environments, this parameter is always determined from the configuration
+of the default Postfix instance.
+</p>
+
+<p> Example: </p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ # NetBSD pkgsrc:
+ <a href="postconf.5.html#openssl_path">openssl_path</a> = /usr/pkg/bin/openssl
+ # Local build:
+ <a href="postconf.5.html#openssl_path">openssl_path</a> = /usr/local/bin/openssl
+</pre>
+</blockquote>
+
+<p>
+This feature is available in Postfix 3.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="owner_request_special">owner_request_special</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Enable special treatment for owner-<i>listname</i> entries in the
+<a href="aliases.5.html">aliases(5)</a> file, and don't split owner-<i>listname</i> and
+<i>listname</i>-request address localparts when the <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>
+is set to "-". This feature is useful for mailing lists.
+</p>
+
+
+</DD>
+
+<DT><b><a name="parent_domain_matches_subdomains">parent_domain_matches_subdomains</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+A list of Postfix features where the pattern "example.com" also
+matches subdomains of example.com,
+instead of requiring an explicit ".example.com" pattern. This is
+planned backwards compatibility: eventually, all Postfix features
+are expected to require explicit ".example.com" style patterns when
+you really want to match subdomains.
+</p>
+
+<p> The following Postfix feature names are supported. </p>
+
+<dl>
+
+<dt> Postfix version 1.0 and later</dt>
+
+<dd>
+<a href="postconf.5.html#debug_peer_list">debug_peer_list</a>,
+<a href="postconf.5.html#fast_flush_domains">fast_flush_domains</a>,
+<a href="postconf.5.html#mynetworks">mynetworks</a>,
+<a href="postconf.5.html#permit_mx_backup_networks">permit_mx_backup_networks</a>,
+<a href="postconf.5.html#relay_domains">relay_domains</a>,
+<a href="postconf.5.html#transport_maps">transport_maps</a>
+</dd>
+
+<dt> Postfix version 1.1 and later</dt>
+
+<dd>
+<a href="postconf.5.html#qmqpd_authorized_clients">qmqpd_authorized_clients</a>,
+smtpd_access_maps,
+</dd>
+
+<dt> Postfix version 2.8 and later </dt>
+
+<dd>
+<a href="postconf.5.html#postscreen_access_list">postscreen_access_list</a>
+</dd>
+
+<dt> Postfix version 3.0 and later </dt>
+
+<dd>
+<a href="postconf.5.html#smtpd_client_event_limit_exceptions">smtpd_client_event_limit_exceptions</a>
+</dd>
+
+</dl>
+
+
+</DD>
+
+<DT><b><a name="permit_mx_backup_networks">permit_mx_backup_networks</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Restrict the use of the <a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> SMTP access feature to
+only domains whose primary MX hosts match the listed networks.
+The parameter value syntax is the same as with the <a href="postconf.5.html#mynetworks">mynetworks</a>
+parameter; note, however, that the default value is empty. </p>
+
+<p> Pattern matching of domain names is controlled by the presence
+or absence of "<a href="postconf.5.html#permit_mx_backup_networks">permit_mx_backup_networks</a>" in the
+<a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a> parameter value. </p>
+
+
+</DD>
+
+<DT><b><a name="pickup_service_name">pickup_service_name</a>
+(default: pickup)</b></DT><DD>
+
+<p>
+The name of the <a href="pickup.8.html">pickup(8)</a> service. This service picks up local mail
+submissions from the Postfix <a href="QSHAPE_README.html#maildrop_queue">maildrop queue</a>.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="pipe_delivery_status_filter">pipe_delivery_status_filter</a>
+(default: $<a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a>)</b></DT><DD>
+
+<p> Optional filter for the <a href="pipe.8.html">pipe(8)</a> delivery agent to change the
+delivery status code or explanatory text of successful or unsuccessful
+deliveries. See <a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a> for details. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="plaintext_reject_code">plaintext_reject_code</a>
+(default: 450)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code when a request
+is rejected by the <b><a href="postconf.5.html#reject_plaintext_session">reject_plaintext_session</a></b> restriction.
+</p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postlog_service_name">postlog_service_name</a>
+(default: postlog)</b></DT><DD>
+
+<p> The name of the <a href="postlogd.8.html">postlogd(8)</a> service entry in <a href="master.5.html">master.cf</a>.
+This service appends logfile records to the file specified
+with the <a href="postconf.5.html#maillog_file">maillog_file</a> parameter. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postlogd_watchdog_timeout">postlogd_watchdog_timeout</a>
+(default: 10s)</b></DT><DD>
+
+<p> How much time a <a href="postlogd.8.html">postlogd(8)</a> process may take to process a request
+before it is terminated by a built-in watchdog timer. This is a
+safety mechanism that prevents <a href="postlogd.8.html">postlogd(8)</a> from becoming non-responsive
+due to a bug in Postfix itself or in system software. This limit
+cannot be set under 10s. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). Time units: s
+(seconds), m (minutes), h (hours), d (days), w (weeks). </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postmulti_control_commands">postmulti_control_commands</a>
+(default: reload flush)</b></DT><DD>
+
+<p> The <a href="postfix.1.html">postfix(1)</a> commands that the <a href="postmulti.1.html">postmulti(1)</a> instance manager
+treats as "control" commands, that operate on running instances. For
+these commands, disabled instances are skipped. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postmulti_start_commands">postmulti_start_commands</a>
+(default: start)</b></DT><DD>
+
+<p> The <a href="postfix.1.html">postfix(1)</a> commands that the <a href="postmulti.1.html">postmulti(1)</a> instance manager treats
+as "start" commands. For these commands, disabled instances are "checked"
+rather than "started", and failure to "start" a member instance of an
+instance group will abort the start-up of later instances. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postmulti_stop_commands">postmulti_stop_commands</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The <a href="postfix.1.html">postfix(1)</a> commands that the <a href="postmulti.1.html">postmulti(1)</a> instance manager treats
+as "stop" commands. For these commands, disabled instances are skipped,
+and enabled instances are processed in reverse order. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_access_list">postscreen_access_list</a>
+(default: <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>)</b></DT><DD>
+
+<p> Permanent white/blacklist for remote SMTP client IP addresses.
+<a href="postscreen.8.html">postscreen(8)</a> searches this list immediately after a remote SMTP
+client connects. Specify a comma- or whitespace-separated list of
+commands (in upper or lower case) or lookup tables. The search stops
+upon the first command that fires for the client IP address. </p>
+
+<dl>
+
+<dt> <b> <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a> </b> </dt> <dd> Whitelist the client and
+terminate the search if the client IP address matches $<a href="postconf.5.html#mynetworks">mynetworks</a>.
+Do not subject the client to any before/after 220 greeting tests.
+Pass the connection immediately to a Postfix SMTP server process.
+<br> Pattern matching of domain names is controlled by the presence
+or absence of "<a href="postconf.5.html#postscreen_access_list">postscreen_access_list</a>" in the
+<a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a> parameter value. </dd>
+
+<dt> <b> <a href="DATABASE_README.html">type:table</a> </b> </dt> <dd> Query the specified lookup
+table. Each table lookup result is an access list, except that
+access lists inside a table cannot specify <a href="DATABASE_README.html">type:table</a> entries. <br>
+To discourage the use of hash, btree, etc. tables, there is no
+support for substring matching like <a href="smtpd.8.html">smtpd(8)</a>. Use CIDR tables
+instead. </dd>
+
+<dt> <b> permit </b> </dt> <dd> Whitelist the client and terminate
+the search. Do not subject the client to any before/after 220
+greeting tests. Pass the connection immediately to a Postfix SMTP
+server process. </dd>
+
+<dt> <b> reject </b> </dt> <dd> Blacklist the client and terminate
+the search. Subject the client to the action configured with the
+<a href="postconf.5.html#postscreen_blacklist_action">postscreen_blacklist_action</a> configuration parameter. </dd>
+
+<dt> <b> dunno </b> </dt> <dd> All <a href="postscreen.8.html">postscreen(8)</a> access lists
+implicitly have this command at the end. <br> When <b> dunno </b>
+is executed inside a lookup table, return from the lookup table and
+evaluate the next command. <br> When <b> dunno </b> is executed
+outside a lookup table, terminate the search, and subject the client
+to the configured before/after 220 greeting tests. </dd>
+
+</dl>
+
+<p> Example: </p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#postscreen_access_list">postscreen_access_list</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>,
+ <a href="cidr_table.5.html">cidr</a>:/etc/postfix/postscreen_access.cidr
+ <a href="postconf.5.html#postscreen_blacklist_action">postscreen_blacklist_action</a> = enforce
+</pre>
+
+<pre>
+/etc/postfix/postscreen_access.<a href="cidr_table.5.html">cidr</a>:
+ # Rules are evaluated in the order as specified.
+ # Blacklist 192.168.* except 192.168.0.1.
+ 192.168.0.1 dunno
+ 192.168.0.0/16 reject
+</pre>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_bare_newline_action">postscreen_bare_newline_action</a>
+(default: ignore)</b></DT><DD>
+
+<p> The action that <a href="postscreen.8.html">postscreen(8)</a> takes when a remote SMTP client sends
+a bare newline character, that is, a newline not preceded by carriage
+return. Specify one of the following: </p>
+
+<dl>
+
+<dt> <b>ignore</b> </dt>
+
+<dd> Ignore the failure of this test. Allow other tests to complete.
+Do <i>not</i> repeat this test before some the result from some
+other test expires.
+This option is useful for testing and collecting statistics
+without blocking mail permanently. </dd>
+
+<dt> <b>enforce</b> </dt>
+
+<dd> Allow other tests to complete. Reject attempts to deliver mail
+with a 550 SMTP reply, and log the helo/sender/recipient information.
+Repeat this test the next time the client connects. </dd>
+
+<dt> <b>drop</b> </dt>
+
+<dd> Drop the connection immediately with a 521 SMTP reply. Repeat
+this test the next time the client connects. </dd>
+
+</dl>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_bare_newline_enable">postscreen_bare_newline_enable</a>
+(default: no)</b></DT><DD>
+
+<p> Enable "bare newline" SMTP protocol tests in the <a href="postscreen.8.html">postscreen(8)</a>
+server. These tests are expensive: a remote SMTP client must
+disconnect after
+it passes the test, before it can talk to a real Postfix SMTP server.
+</p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_bare_newline_ttl">postscreen_bare_newline_ttl</a>
+(default: 30d)</b></DT><DD>
+
+<p> The amount of time that <a href="postscreen.8.html">postscreen(8)</a> will use the result from
+a successful "bare newline" SMTP protocol test. During this
+time, the client IP address is excluded from this test. The default
+is long because a remote SMTP client must disconnect after it passes
+the test,
+before it can talk to a real Postfix SMTP server. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). Time units: s
+(seconds), m (minutes), h (hours), d (days), w (weeks). </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_blacklist_action">postscreen_blacklist_action</a>
+(default: ignore)</b></DT><DD>
+
+<p> The action that <a href="postscreen.8.html">postscreen(8)</a> takes when a remote SMTP client is
+permanently blacklisted with the <a href="postconf.5.html#postscreen_access_list">postscreen_access_list</a> parameter.
+Specify one of the following: </p>
+
+<dl>
+
+<dt> <b>ignore</b> (default) </dt>
+
+<dd> Ignore this result. Allow other tests to complete. Repeat
+this test the next time the client connects.
+This option is useful for testing and collecting statistics
+without blocking mail. </dd>
+
+<dt> <b>enforce</b> </dt>
+
+<dd> Allow other tests to complete. Reject attempts to deliver mail
+with a 550 SMTP reply, and log the helo/sender/recipient information.
+Repeat this test the next time the client connects. </dd>
+
+<dt> <b>drop</b> </dt>
+
+<dd> Drop the connection immediately with a 521 SMTP reply. Repeat
+this test the next time the client connects. </dd>
+
+</dl>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_cache_cleanup_interval">postscreen_cache_cleanup_interval</a>
+(default: 12h)</b></DT><DD>
+
+<p> The amount of time between <a href="postscreen.8.html">postscreen(8)</a> cache cleanup runs.
+Cache cleanup increases the load on the cache database and should
+therefore not be run frequently. This feature requires that the
+cache database supports the "delete" and "sequence" operators.
+Specify a zero interval to disable cache cleanup. </p>
+
+<p> After each cache cleanup run, the <a href="postscreen.8.html">postscreen(8)</a> daemon logs the
+number of entries that were retained and dropped. A cleanup run is
+logged as "partial" when the daemon terminates early after "<b>postfix
+reload</b>", "<b>postfix stop</b>", or no requests for $<a href="postconf.5.html#max_idle">max_idle</a>
+seconds. </p>
+
+<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
+(weeks). </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_cache_map">postscreen_cache_map</a>
+(default: <a href="DATABASE_README.html#types">btree</a>:$<a href="postconf.5.html#data_directory">data_directory</a>/postscreen_cache)</b></DT><DD>
+
+<p> Persistent storage for the <a href="postscreen.8.html">postscreen(8)</a> server decisions. </p>
+
+<p> To share a <a href="postscreen.8.html">postscreen(8)</a> cache between multiple <a href="postscreen.8.html">postscreen(8)</a>
+instances, use "<a href="postconf.5.html#postscreen_cache_map">postscreen_cache_map</a> = <a href="proxymap.8.html">proxy</a>:<a href="DATABASE_README.html#types">btree</a>:/path/to/file".
+This requires Postfix version 2.9 or later; earlier <a href="proxymap.8.html">proxymap(8)</a>
+implementations don't support cache cleanup. For an alternative
+approach see the <a href="memcache_table.5.html">memcache_table(5)</a> manpage. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_cache_retention_time">postscreen_cache_retention_time</a>
+(default: 7d)</b></DT><DD>
+
+<p> The amount of time that <a href="postscreen.8.html">postscreen(8)</a> will cache an expired
+temporary whitelist entry before it is removed. This prevents clients
+from being logged as "NEW" just because their cache entry expired
+an hour ago. It also prevents the cache from filling up with clients
+that passed some deep protocol test once and never came back. </p>
+
+<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
+(weeks). </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_client_connection_count_limit">postscreen_client_connection_count_limit</a>
+(default: $<a href="postconf.5.html#smtpd_client_connection_count_limit">smtpd_client_connection_count_limit</a>)</b></DT><DD>
+
+<p> How many simultaneous connections any remote SMTP client is
+allowed to have
+with the <a href="postscreen.8.html">postscreen(8)</a> daemon. By default, this limit is the same
+as with the Postfix SMTP server. Note that the triage process can
+take several seconds, with the time spent in <a href="postconf.5.html#postscreen_greet_wait">postscreen_greet_wait</a>
+delay, and with the time spent talking to the <a href="postscreen.8.html">postscreen(8)</a> built-in
+dummy SMTP protocol engine. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_command_count_limit">postscreen_command_count_limit</a>
+(default: 20)</b></DT><DD>
+
+<p> The limit on the total number of commands per SMTP session for
+<a href="postscreen.8.html">postscreen(8)</a>'s built-in SMTP protocol engine. This SMTP engine
+defers or rejects all attempts to deliver mail, therefore there is
+no need to enforce separate limits on the number of junk commands
+and error commands. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_command_filter">postscreen_command_filter</a>
+(default: $<a href="postconf.5.html#smtpd_command_filter">smtpd_command_filter</a>)</b></DT><DD>
+
+<p> A mechanism to transform commands from remote SMTP clients.
+See <a href="postconf.5.html#smtpd_command_filter">smtpd_command_filter</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_command_time_limit">postscreen_command_time_limit</a>
+(default: normal: 300s, overload: 10s)</b></DT><DD>
+
+<p> The time limit to read an entire command line with <a href="postscreen.8.html">postscreen(8)</a>'s
+built-in SMTP protocol engine. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_disable_vrfy_command">postscreen_disable_vrfy_command</a>
+(default: $<a href="postconf.5.html#disable_vrfy_command">disable_vrfy_command</a>)</b></DT><DD>
+
+<p> Disable the SMTP VRFY command in the <a href="postscreen.8.html">postscreen(8)</a> daemon. See
+<a href="postconf.5.html#disable_vrfy_command">disable_vrfy_command</a> for details. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_discard_ehlo_keyword_address_maps">postscreen_discard_ehlo_keyword_address_maps</a>
+(default: $<a href="postconf.5.html#smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a>)</b></DT><DD>
+
+<p> Lookup tables, indexed by the remote SMTP client address, with
+case insensitive lists of EHLO keywords (pipelining, starttls, auth,
+etc.) that the <a href="postscreen.8.html">postscreen(8)</a> server will not send in the EHLO response
+to a remote SMTP client. See <a href="postconf.5.html#smtpd_discard_ehlo_keywords">smtpd_discard_ehlo_keywords</a> for details.
+The table is not searched by hostname for robustness reasons. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_discard_ehlo_keywords">postscreen_discard_ehlo_keywords</a>
+(default: $<a href="postconf.5.html#smtpd_discard_ehlo_keywords">smtpd_discard_ehlo_keywords</a>)</b></DT><DD>
+
+<p> A case insensitive list of EHLO keywords (pipelining, starttls,
+auth, etc.) that the <a href="postscreen.8.html">postscreen(8)</a> server will not send in the EHLO
+response to a remote SMTP client. See <a href="postconf.5.html#smtpd_discard_ehlo_keywords">smtpd_discard_ehlo_keywords</a>
+for details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_dnsbl_action">postscreen_dnsbl_action</a>
+(default: ignore)</b></DT><DD>
+
+<p>The action that <a href="postscreen.8.html">postscreen(8)</a> takes when a remote SMTP client's combined
+DNSBL score is equal to or greater than a threshold (as defined
+with the <a href="postconf.5.html#postscreen_dnsbl_sites">postscreen_dnsbl_sites</a> and <a href="postconf.5.html#postscreen_dnsbl_threshold">postscreen_dnsbl_threshold</a>
+parameters). Specify one of the following: </p>
+
+<dl>
+
+<dt> <b>ignore</b> (default) </dt>
+
+<dd> Ignore the failure of this test. Allow other tests to complete.
+Repeat this test the next time the client connects.
+This option is useful for testing and collecting statistics
+without blocking mail. </dd>
+
+<dt> <b>enforce</b> </dt>
+
+<dd> Allow other tests to complete. Reject attempts to deliver mail
+with a 550 SMTP reply, and log the helo/sender/recipient information.
+Repeat this test the next time the client connects. </dd>
+
+<dt> <b>drop</b> </dt>
+
+<dd> Drop the connection immediately with a 521 SMTP reply. Repeat
+this test the next time the client connects. </dd>
+
+</dl>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_dnsbl_max_ttl">postscreen_dnsbl_max_ttl</a>
+(default: ${<a href="postconf.5.html#postscreen_dnsbl_ttl">postscreen_dnsbl_ttl</a>?{$<a href="postconf.5.html#postscreen_dnsbl_ttl">postscreen_dnsbl_ttl</a>}:{1}}h)</b></DT><DD>
+
+<p> The maximum amount of time that <a href="postscreen.8.html">postscreen(8)</a> will use the
+result from a successful DNS-based reputation test before a
+client IP address is required to pass that test again. If the DNS
+reply specifies a shorter TTL value, that value will be used unless
+it would be smaller than <a href="postconf.5.html#postscreen_dnsbl_min_ttl">postscreen_dnsbl_min_ttl</a>. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). Time units: s
+(seconds), m (minutes), h (hours), d (days), w (weeks). </p>
+
+<p> This feature is available in Postfix 3.1. The default setting
+is backwards-compatible with older Postfix versions. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_dnsbl_min_ttl">postscreen_dnsbl_min_ttl</a>
+(default: 60s)</b></DT><DD>
+
+<p> The minimum amount of time that <a href="postscreen.8.html">postscreen(8)</a> will use the
+result from a successful DNS-based reputation test before a
+client IP address is required to pass that test again. If the DNS
+reply specifies a larger TTL value, that value will be used unless
+it would be larger than <a href="postconf.5.html#postscreen_dnsbl_max_ttl">postscreen_dnsbl_max_ttl</a>. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). Time units: s
+(seconds), m (minutes), h (hours), d (days), w (weeks). </p>
+
+<p> This feature is available in Postfix 3.1. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_dnsbl_reply_map">postscreen_dnsbl_reply_map</a>
+(default: empty)</b></DT><DD>
+
+<p> A mapping from actual DNSBL domain name which includes a secret
+password, to the DNSBL domain name that postscreen will reply with
+when it rejects mail. When no mapping is found, the actual DNSBL
+domain will be used. </p>
+
+<p> For maximal stability it is best to use a file that is read
+into memory such as <a href="pcre_table.5.html">pcre</a>:, <a href="regexp_table.5.html">regexp</a>: or <a href="DATABASE_README.html#types">texthash</a>: (<a href="DATABASE_README.html#types">texthash</a>: is similar
+to <a href="DATABASE_README.html#types">hash</a>:, except a) there is no need to run <a href="postmap.1.html">postmap(1)</a> before the
+file can be used, and b) <a href="DATABASE_README.html#types">texthash</a>: does not detect changes after
+the file is read). </p>
+
+<p> Example: </p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#postscreen_dnsbl_reply_map">postscreen_dnsbl_reply_map</a> = <a href="DATABASE_README.html#types">texthash</a>:/etc/postfix/dnsbl_reply
+</pre>
+
+<pre>
+/etc/postfix/dnsbl_reply:
+ secret.zen.spamhaus.org zen.spamhaus.org
+</pre>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_dnsbl_sites">postscreen_dnsbl_sites</a>
+(default: empty)</b></DT><DD>
+
+<p>Optional list of DNS white/blacklist domains, filters and weight
+factors. When the list is non-empty, the <a href="dnsblog.8.html">dnsblog(8)</a> daemon will
+query these domains with the IP addresses of remote SMTP clients,
+and <a href="postscreen.8.html">postscreen(8)</a> will update an SMTP client's DNSBL score with
+each non-error reply. </p>
+
+<p> Caution: when postscreen rejects mail, it replies with the DNSBL
+domain name. Use the <a href="postconf.5.html#postscreen_dnsbl_reply_map">postscreen_dnsbl_reply_map</a> feature to hide
+"password" information in DNSBL domain names. </p>
+
+<p> When a client's score is equal to or greater than the threshold
+specified with <a href="postconf.5.html#postscreen_dnsbl_threshold">postscreen_dnsbl_threshold</a>, <a href="postscreen.8.html">postscreen(8)</a> can drop
+the connection with the remote SMTP client. </p>
+
+<p> Specify a list of domain=filter*weight entries, separated by
+comma or whitespace. </p>
+
+<ul>
+
+<li> <p> When no "=filter" is specified, <a href="postscreen.8.html">postscreen(8)</a> will use any
+non-error DNSBL reply. Otherwise, <a href="postscreen.8.html">postscreen(8)</a> uses only DNSBL
+replies that match the filter. The filter has the form d.d.d.d,
+where each d is a number, or a pattern inside [] that contains one
+or more ";"-separated numbers or number..number ranges. </p>
+
+<li> <p> When no "*weight" is specified, <a href="postscreen.8.html">postscreen(8)</a> increments
+the remote SMTP client's DNSBL score by 1. Otherwise, the weight must be
+an integral number, and <a href="postscreen.8.html">postscreen(8)</a> adds the specified weight to
+the remote SMTP client's DNSBL score. Specify a negative number for
+whitelisting. </p>
+
+<li> <p> When one <a href="postconf.5.html#postscreen_dnsbl_sites">postscreen_dnsbl_sites</a> entry produces multiple
+DNSBL responses, <a href="postscreen.8.html">postscreen(8)</a> applies the weight at most once.
+</p>
+
+</ul>
+
+<p> Examples: </p>
+
+<p> To use example.com as a high-confidence blocklist, and to
+block mail with example.net and example.org only when both agree:
+</p>
+
+<pre>
+<a href="postconf.5.html#postscreen_dnsbl_threshold">postscreen_dnsbl_threshold</a> = 2
+<a href="postconf.5.html#postscreen_dnsbl_sites">postscreen_dnsbl_sites</a> = example.com*2, example.net, example.org
+</pre>
+
+<p> To filter only DNSBL replies containing 127.0.0.4: </p>
+
+<pre>
+<a href="postconf.5.html#postscreen_dnsbl_sites">postscreen_dnsbl_sites</a> = example.com=127.0.0.4
+</pre>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_dnsbl_threshold">postscreen_dnsbl_threshold</a>
+(default: 1)</b></DT><DD>
+
+<p> The inclusive lower bound for blocking a remote SMTP client, based on
+its combined DNSBL score as defined with the <a href="postconf.5.html#postscreen_dnsbl_sites">postscreen_dnsbl_sites</a>
+parameter. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_dnsbl_timeout">postscreen_dnsbl_timeout</a>
+(default: 10s)</b></DT><DD>
+
+<p> The time limit for DNSBL or DNSWL lookups. This is separate from
+the timeouts in the <a href="dnsblog.8.html">dnsblog(8)</a> daemon which are defined by system
+resolver(3) routines. </p>
+
+<p> This feature is available in Postfix 3.0. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_dnsbl_ttl">postscreen_dnsbl_ttl</a>
+(default: 1h)</b></DT><DD>
+
+<p> The amount of time that <a href="postscreen.8.html">postscreen(8)</a> will use the result from
+a successful DNS-based reputation test before a client
+IP address is required to pass that test again. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). Time units: s
+(seconds), m (minutes), h (hours), d (days), w (weeks). </p>
+
+<p> This feature is available in Postfix 2.8-3.0. It was
+replaced by <a href="postconf.5.html#postscreen_dnsbl_max_ttl">postscreen_dnsbl_max_ttl</a> in Postfix 3.1. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_dnsbl_whitelist_threshold">postscreen_dnsbl_whitelist_threshold</a>
+(default: 0)</b></DT><DD>
+
+<p> Allow a remote SMTP client to skip "before" and "after 220
+greeting" protocol tests, based on its combined DNSBL score as
+defined with the <a href="postconf.5.html#postscreen_dnsbl_sites">postscreen_dnsbl_sites</a> parameter. </p>
+
+<p> Specify a negative value to enable this feature. When a client
+passes the <a href="postconf.5.html#postscreen_dnsbl_whitelist_threshold">postscreen_dnsbl_whitelist_threshold</a> without having
+failed other tests, all pending or disabled tests are flagged as
+completed with a time-to-live value equal to <a href="postconf.5.html#postscreen_dnsbl_ttl">postscreen_dnsbl_ttl</a>.
+When a test was already completed, its time-to-live value is updated
+if it was less than <a href="postconf.5.html#postscreen_dnsbl_ttl">postscreen_dnsbl_ttl</a>. </p>
+
+<p> This feature is available in Postfix 2.11. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_enforce_tls">postscreen_enforce_tls</a>
+(default: $<a href="postconf.5.html#smtpd_enforce_tls">smtpd_enforce_tls</a>)</b></DT><DD>
+
+<p> Mandatory TLS: announce STARTTLS support to remote SMTP clients, and
+require that clients use TLS encryption. See smtpd_postscreen_enforce_tls
+for details. </p>
+
+<p> This feature is available in Postfix 2.8 and later.
+Preferably, use <a href="postconf.5.html#postscreen_tls_security_level">postscreen_tls_security_level</a> instead. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_expansion_filter">postscreen_expansion_filter</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> List of characters that are permitted in <a href="postconf.5.html#postscreen_reject_footer">postscreen_reject_footer</a>
+attribute expansions. See <a href="postconf.5.html#smtpd_expansion_filter">smtpd_expansion_filter</a> for further
+details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_forbidden_commands">postscreen_forbidden_commands</a>
+(default: $<a href="postconf.5.html#smtpd_forbidden_commands">smtpd_forbidden_commands</a>)</b></DT><DD>
+
+<p> List of commands that the <a href="postscreen.8.html">postscreen(8)</a> server considers in
+violation of the SMTP protocol. See <a href="postconf.5.html#smtpd_forbidden_commands">smtpd_forbidden_commands</a> for
+syntax, and <a href="postconf.5.html#postscreen_non_smtp_command_action">postscreen_non_smtp_command_action</a> for possible actions.
+</p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_greet_action">postscreen_greet_action</a>
+(default: ignore)</b></DT><DD>
+
+<p>The action that <a href="postscreen.8.html">postscreen(8)</a> takes when a remote SMTP client speaks
+before its turn within the time specified with the <a href="postconf.5.html#postscreen_greet_wait">postscreen_greet_wait</a>
+parameter. Specify one of the following: </p>
+
+<dl>
+
+<dt> <b>ignore</b> (default) </dt>
+
+<dd> Ignore the failure of this test. Allow other tests to complete.
+Repeat this test the next time the client connects.
+This option is useful for testing and collecting statistics
+without blocking mail. </dd>
+
+<dt> <b>enforce</b> </dt>
+
+<dd> Allow other tests to complete. Reject attempts to deliver mail
+with a 550 SMTP reply, and log the helo/sender/recipient information.
+Repeat this test the next time the client connects. </dd>
+
+<dt> <b>drop</b> </dt>
+
+<dd> Drop the connection immediately with a 521 SMTP reply. Repeat
+this test the next time the client connects. </dd>
+
+</dl>
+
+<p> In either case, <a href="postscreen.8.html">postscreen(8)</a> will not whitelist the remote SMTP client
+IP address. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_greet_banner">postscreen_greet_banner</a>
+(default: $<a href="postconf.5.html#smtpd_banner">smtpd_banner</a>)</b></DT><DD>
+
+<p> The <i>text</i> in the optional "220-<i>text</i>..." server
+response that
+<a href="postscreen.8.html">postscreen(8)</a> sends ahead of the real Postfix SMTP server's "220
+text..." response, in an attempt to confuse bad SMTP clients so
+that they speak before their turn (pre-greet). Specify an empty
+value to disable this feature. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_greet_ttl">postscreen_greet_ttl</a>
+(default: 1d)</b></DT><DD>
+
+<p> The amount of time that <a href="postscreen.8.html">postscreen(8)</a> will use the result from
+a successful PREGREET test. During this time, the client IP address
+is excluded from this test. The default is relatively short, because
+a good client can immediately talk to a real Postfix SMTP server. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). Time units: s
+(seconds), m (minutes), h (hours), d (days), w (weeks). </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_greet_wait">postscreen_greet_wait</a>
+(default: normal: 6s, overload: 2s)</b></DT><DD>
+
+<p> The amount of time that <a href="postscreen.8.html">postscreen(8)</a> will wait for an SMTP
+client to send a command before its turn, and for DNS blocklist
+lookup results to arrive (default: up to 2 seconds under stress,
+up to 6 seconds otherwise). <p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). </p>
+
+<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
+(weeks). </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_helo_required">postscreen_helo_required</a>
+(default: $<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a>)</b></DT><DD>
+
+<p> Require that a remote SMTP client sends HELO or EHLO before
+commencing a MAIL transaction. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_non_smtp_command_action">postscreen_non_smtp_command_action</a>
+(default: drop)</b></DT><DD>
+
+<p> The action that <a href="postscreen.8.html">postscreen(8)</a> takes when a remote SMTP client sends
+non-SMTP commands as specified with the <a href="postconf.5.html#postscreen_forbidden_commands">postscreen_forbidden_commands</a>
+parameter. Specify one of the following: </p>
+
+<dl>
+
+<dt> <b>ignore</b> </dt>
+
+<dd> Ignore the failure of this test. Allow other tests to complete.
+Do <i>not</i> repeat this test before some the result from some
+other test expires.
+This option is useful for testing and collecting statistics
+without blocking mail permanently. </dd>
+
+<dt> <b>enforce</b> </dt>
+
+<dd> Allow other tests to complete. Reject attempts to deliver mail
+with a 550 SMTP reply, and log the helo/sender/recipient information.
+Repeat this test the next time the client connects. </dd>
+
+<dt> <b>drop</b> </dt>
+
+<dd> Drop the connection immediately with a 521 SMTP reply. Repeat
+this test the next time the client connects. This action is the
+same as with the Postfix SMTP server's <a href="postconf.5.html#smtpd_forbidden_commands">smtpd_forbidden_commands</a>
+feature. </dd>
+
+</dl>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_non_smtp_command_enable">postscreen_non_smtp_command_enable</a>
+(default: no)</b></DT><DD>
+
+<p> Enable "non-SMTP command" tests in the <a href="postscreen.8.html">postscreen(8)</a> server. These
+tests are expensive: a client must disconnect after it passes the
+test, before it can talk to a real Postfix SMTP server. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_non_smtp_command_ttl">postscreen_non_smtp_command_ttl</a>
+(default: 30d)</b></DT><DD>
+
+<p> The amount of time that <a href="postscreen.8.html">postscreen(8)</a> will use the result from
+a successful "non_smtp_command" SMTP protocol test. During this
+time, the client IP address is excluded from this test. The default
+is long because a client must disconnect after it passes the test,
+before it can talk to a real Postfix SMTP server. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). Time units: s
+(seconds), m (minutes), h (hours), d (days), w (weeks). </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_pipelining_action">postscreen_pipelining_action</a>
+(default: enforce)</b></DT><DD>
+
+<p> The action that <a href="postscreen.8.html">postscreen(8)</a> takes when a remote SMTP client
+sends
+multiple commands instead of sending one command and waiting for
+the server to respond. Specify one of the following: </p>
+
+<dl>
+
+<dt> <b>ignore</b> </dt>
+
+<dd> Ignore the failure of this test. Allow other tests to complete.
+Do <i>not</i> repeat this test before some the result from some
+other test expires.
+This option is useful for testing and collecting statistics
+without blocking mail permanently. </dd>
+
+<dt> <b>enforce</b> </dt>
+
+<dd> Allow other tests to complete. Reject attempts to deliver mail
+with a 550 SMTP reply, and log the helo/sender/recipient information.
+Repeat this test the next time the client connects. </dd>
+
+<dt> <b>drop</b> </dt>
+
+<dd> Drop the connection immediately with a 521 SMTP reply. Repeat
+this test the next time the client connects. </dd>
+
+</dl>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_pipelining_enable">postscreen_pipelining_enable</a>
+(default: no)</b></DT><DD>
+
+<p> Enable "pipelining" SMTP protocol tests in the <a href="postscreen.8.html">postscreen(8)</a>
+server. These tests are expensive: a good client must disconnect
+after it passes the test, before it can talk to a real Postfix SMTP
+server. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_pipelining_ttl">postscreen_pipelining_ttl</a>
+(default: 30d)</b></DT><DD>
+
+<p> The amount of time that <a href="postscreen.8.html">postscreen(8)</a> will use the result from
+a successful "pipelining" SMTP protocol test. During this time, the
+client IP address is excluded from this test. The default is
+long because a good client must disconnect after it passes the test,
+before it can talk to a real Postfix SMTP server. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). Time units: s
+(seconds), m (minutes), h (hours), d (days), w (weeks). </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_post_queue_limit">postscreen_post_queue_limit</a>
+(default: $<a href="postconf.5.html#default_process_limit">default_process_limit</a>)</b></DT><DD>
+
+<p> The number of clients that can be waiting for service from a
+real Postfix SMTP server process. When this queue is full, all
+clients will
+receive a 421 response. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_pre_queue_limit">postscreen_pre_queue_limit</a>
+(default: $<a href="postconf.5.html#default_process_limit">default_process_limit</a>)</b></DT><DD>
+
+<p> The number of non-whitelisted clients that can be waiting for
+a decision whether they will receive service from a real Postfix
+SMTP server
+process. When this queue is full, all non-whitelisted clients will
+receive a 421 response. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_reject_footer">postscreen_reject_footer</a>
+(default: $<a href="postconf.5.html#smtpd_reject_footer">smtpd_reject_footer</a>)</b></DT><DD>
+
+<p> Optional information that is appended after a 4XX or 5XX
+<a href="postscreen.8.html">postscreen(8)</a> server
+response. See <a href="postconf.5.html#smtpd_reject_footer">smtpd_reject_footer</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_reject_footer_maps">postscreen_reject_footer_maps</a>
+(default: $<a href="postconf.5.html#smtpd_reject_footer_maps">smtpd_reject_footer_maps</a>)</b></DT><DD>
+
+<p> Optional lookup table for information that is appended after a 4XX
+or 5XX <a href="postscreen.8.html">postscreen(8)</a> server response. See <a href="postconf.5.html#smtpd_reject_footer_maps">smtpd_reject_footer_maps</a> for
+further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_tls_security_level">postscreen_tls_security_level</a>
+(default: $<a href="postconf.5.html#smtpd_tls_security_level">smtpd_tls_security_level</a>)</b></DT><DD>
+
+<p> The SMTP TLS security level for the <a href="postscreen.8.html">postscreen(8)</a> server; when
+a non-empty value is specified, this overrides the obsolete parameters
+<a href="postconf.5.html#postscreen_use_tls">postscreen_use_tls</a> and <a href="postconf.5.html#postscreen_enforce_tls">postscreen_enforce_tls</a>. See <a href="postconf.5.html#smtpd_tls_security_level">smtpd_tls_security_level</a>
+for details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_upstream_proxy_protocol">postscreen_upstream_proxy_protocol</a>
+(default: empty)</b></DT><DD>
+
+<p> The name of the proxy protocol used by an optional before-postscreen
+proxy agent. When a proxy agent is used, this protocol conveys local
+and remote address and port information. Specify
+"<a href="postconf.5.html#postscreen_upstream_proxy_protocol">postscreen_upstream_proxy_protocol</a> = haproxy" to enable the haproxy
+protocol. <p>
+
+<p> This feature is available in Postfix 2.10 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_upstream_proxy_timeout">postscreen_upstream_proxy_timeout</a>
+(default: 5s)</b></DT><DD>
+
+<p> The time limit for the proxy protocol specified with the
+<a href="postconf.5.html#postscreen_upstream_proxy_protocol">postscreen_upstream_proxy_protocol</a> parameter. </p>
+
+<p> This feature is available in Postfix 2.10 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_use_tls">postscreen_use_tls</a>
+(default: $<a href="postconf.5.html#smtpd_use_tls">smtpd_use_tls</a>)</b></DT><DD>
+
+<p> Opportunistic TLS: announce STARTTLS support to remote SMTP clients,
+but do not require that clients use TLS encryption. </p>
+
+<p> This feature is available in Postfix 2.8 and later.
+Preferably, use <a href="postconf.5.html#postscreen_tls_security_level">postscreen_tls_security_level</a> instead. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_watchdog_timeout">postscreen_watchdog_timeout</a>
+(default: 10s)</b></DT><DD>
+
+<p> How much time a <a href="postscreen.8.html">postscreen(8)</a> process may take to respond to
+a remote SMTP client command or to perform a cache operation before it
+is terminated by a built-in watchdog timer. This is a safety
+mechanism that prevents <a href="postscreen.8.html">postscreen(8)</a> from becoming non-responsive
+due to a bug in Postfix itself or in system software. To avoid
+false alarms and unnecessary cache corruption this limit cannot be
+set under 10s. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). Time units: s
+(seconds), m (minutes), h (hours), d (days), w (weeks). </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="postscreen_whitelist_interfaces">postscreen_whitelist_interfaces</a>
+(default: <a href="DATABASE_README.html#types">static</a>:all)</b></DT><DD>
+
+<p> A list of local <a href="postscreen.8.html">postscreen(8)</a> server IP addresses where a
+non-whitelisted remote SMTP client can obtain <a href="postscreen.8.html">postscreen(8)</a>'s temporary
+whitelist status. This status is required before the client can
+talk to a Postfix SMTP server process. By default, a client can
+obtain <a href="postscreen.8.html">postscreen(8)</a>'s whitelist status on any local <a href="postscreen.8.html">postscreen(8)</a>
+server IP address. </p>
+
+<p> When <a href="postscreen.8.html">postscreen(8)</a> listens on both primary and backup MX
+addresses, the <a href="postconf.5.html#postscreen_whitelist_interfaces">postscreen_whitelist_interfaces</a> parameter can be
+configured to give the temporary whitelist status only when a client
+connects to a primary MX address. Once a client is whitelisted it
+can talk to a Postfix SMTP server on any address. Thus, clients
+that connect only to backup MX addresses will never become whitelisted,
+and will never be allowed to talk to a Postfix SMTP server process.
+</p>
+
+<p> Specify a list of network addresses or network/netmask patterns,
+separated by commas and/or whitespace. The netmask specifies the
+number of bits in the network part of a host address. Continue long
+lines by starting the next line with whitespace. </p>
+
+<p> You can also specify "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns. A
+"/file/name" pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>"
+lookup table is matched when a table entry matches a lookup string
+(the lookup result is ignored). </p>
+
+<p> The list is matched left to right, and the search stops on the
+first match. Specify "!pattern" to exclude an address or network
+block from the list. </p>
+
+<p> Note: IP version 6 address information must be specified inside
+[] in the <a href="postconf.5.html#postscreen_whitelist_interfaces">postscreen_whitelist_interfaces</a> value, and in files
+specified with "/file/name". IP version 6 addresses contain the
+":" character, and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>"
+pattern. </p>
+
+<p> Example: </p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ # Don't whitelist connections to the backup IP address.
+ <a href="postconf.5.html#postscreen_whitelist_interfaces">postscreen_whitelist_interfaces</a> = !168.100.189.8, <a href="DATABASE_README.html#types">static</a>:all
+</pre>
+
+<p> This feature is available in Postfix 2.9 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="prepend_delivered_header">prepend_delivered_header</a>
+(default: command, file, forward)</b></DT><DD>
+
+<p> The message delivery contexts where the Postfix <a href="local.8.html">local(8)</a> delivery
+agent prepends a Delivered-To: message header with the address
+that the mail was delivered to. This information is used for mail
+delivery loop detection. </p>
+
+<p>
+By default, the Postfix local delivery agent prepends a Delivered-To:
+header when forwarding mail and when delivering to file (mailbox)
+and command. Turning off the Delivered-To: header when forwarding
+mail is not recommended.
+</p>
+
+<p>
+Specify zero or more of <b>forward</b>, <b>file</b>, or <b>command</b>.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#prepend_delivered_header">prepend_delivered_header</a> = forward
+</pre>
+
+
+</DD>
+
+<DT><b><a name="process_id">process_id</a>
+(read-only)</b></DT><DD>
+
+<p>
+The process ID of a Postfix command or daemon process.
+</p>
+
+
+</DD>
+
+<DT><b><a name="process_id_directory">process_id_directory</a>
+(default: pid)</b></DT><DD>
+
+<p>
+The location of Postfix PID files relative to $<a href="postconf.5.html#queue_directory">queue_directory</a>.
+This is a read-only parameter.
+</p>
+
+
+</DD>
+
+<DT><b><a name="process_name">process_name</a>
+(read-only)</b></DT><DD>
+
+<p>
+The process name of a Postfix command or daemon process.
+</p>
+
+
+</DD>
+
+<DT><b><a name="propagate_unmatched_extensions">propagate_unmatched_extensions</a>
+(default: canonical, virtual)</b></DT><DD>
+
+<p>
+What address lookup tables copy an address extension from the lookup
+key to the lookup result.
+</p>
+
+<p>
+For example, with a <a href="virtual.5.html">virtual(5)</a> mapping of "<i>joe@example.com =&gt;
+joe.user@example.net</i>", the address "<i>joe+foo@example.com</i>"
+would rewrite to "<i>joe.user+foo@example.net</i>".
+</p>
+
+<p>
+Specify zero or more of <b>canonical</b>, <b>virtual</b>, <b>alias</b>,
+<b>forward</b>, <b>include</b> or <b>generic</b>. These cause
+address extension
+propagation with <a href="canonical.5.html">canonical(5)</a>, <a href="virtual.5.html">virtual(5)</a>, and <a href="aliases.5.html">aliases(5)</a> maps,
+with <a href="local.8.html">local(8)</a> .forward and :include: file lookups, and with <a href="smtp.8.html">smtp(8)</a>
+generic maps, respectively. </p>
+
+<p>
+Note: enabling this feature for types other than <b>canonical</b>
+and <b>virtual</b> is likely to cause problems when mail is forwarded
+to other sites, especially with mail that is sent to a mailing list
+exploder address.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#propagate_unmatched_extensions">propagate_unmatched_extensions</a> = canonical, virtual, alias,
+ forward, include
+<a href="postconf.5.html#propagate_unmatched_extensions">propagate_unmatched_extensions</a> = canonical, virtual
+</pre>
+
+
+</DD>
+
+<DT><b><a name="proxy_interfaces">proxy_interfaces</a>
+(default: empty)</b></DT><DD>
+
+<p>
+The network interface addresses that this mail system receives mail
+on by way of a proxy or network address translation unit.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+<p> You must specify your "outside" proxy/NAT addresses when your
+system is a backup MX host for other domains, otherwise mail delivery
+loops will happen when the primary MX host is down. </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a> = 1.2.3.4
+</pre>
+
+
+</DD>
+
+<DT><b><a name="proxy_read_maps">proxy_read_maps</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The lookup tables that the <a href="proxymap.8.html">proxymap(8)</a> server is allowed to
+access for the read-only service.
+</p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma.
+Table references that don't begin with <a href="proxymap.8.html">proxy</a>: are ignored.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="proxy_write_maps">proxy_write_maps</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The lookup tables that the <a href="proxymap.8.html">proxymap(8)</a> server is allowed to
+access for the read-write service. Postfix-owned local database
+files should be stored under the Postfix-owned <a href="postconf.5.html#data_directory">data_directory</a>.
+Table references that don't begin with <a href="proxymap.8.html">proxy</a>: are ignored. </p>
+
+<p>
+This feature is available in Postfix 2.5 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="proxymap_service_name">proxymap_service_name</a>
+(default: proxymap)</b></DT><DD>
+
+<p> The name of the proxymap read-only table lookup service. This
+service is normally implemented by the <a href="proxymap.8.html">proxymap(8)</a> daemon. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="proxywrite_service_name">proxywrite_service_name</a>
+(default: proxywrite)</b></DT><DD>
+
+<p> The name of the proxywrite read-write table lookup service.
+This service is normally implemented by the <a href="proxymap.8.html">proxymap(8)</a> daemon.
+</p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="qmgr_clog_warn_time">qmgr_clog_warn_time</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The minimal delay between warnings that a specific destination is
+clogging up the Postfix <a href="QSHAPE_README.html#active_queue">active queue</a>. Specify 0 to disable.
+</p>
+
+<p>
+This feature is enabled with the <a href="postconf.5.html#helpful_warnings">helpful_warnings</a> parameter.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="qmgr_daemon_timeout">qmgr_daemon_timeout</a>
+(default: 1000s)</b></DT><DD>
+
+<p> How much time a Postfix queue manager process may take to handle
+a request before it is terminated by a built-in watchdog timer.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="qmgr_fudge_factor">qmgr_fudge_factor</a>
+(default: 100)</b></DT><DD>
+
+<p>
+Obsolete feature: the percentage of delivery resources that a busy
+mail system will use up for delivery of a large mailing list
+message.
+</p>
+
+<p>
+This feature exists only in the <a href="qmgr.8.html">oqmgr(8)</a> old queue manager. The
+current queue manager solves the problem in a better way.
+</p>
+
+
+</DD>
+
+<DT><b><a name="qmgr_ipc_timeout">qmgr_ipc_timeout</a>
+(default: 60s)</b></DT><DD>
+
+<p> The time limit for the queue manager to send or receive information
+over an internal communication channel. The purpose is to break
+out of deadlock situations. If the time limit is exceeded the
+software either retries or aborts the operation. </p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="qmgr_message_active_limit">qmgr_message_active_limit</a>
+(default: 20000)</b></DT><DD>
+
+<p>
+The maximal number of messages in the <a href="QSHAPE_README.html#active_queue">active queue</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="qmgr_message_recipient_limit">qmgr_message_recipient_limit</a>
+(default: 20000)</b></DT><DD>
+
+<p> The maximal number of recipients held in memory by the Postfix
+queue manager, and the maximal size of the short-term,
+in-memory "dead" destination status cache. </p>
+
+
+</DD>
+
+<DT><b><a name="qmgr_message_recipient_minimum">qmgr_message_recipient_minimum</a>
+(default: 10)</b></DT><DD>
+
+<p>
+The minimal number of in-memory recipients for any message. This
+takes priority over any other in-memory recipient limits (i.e.,
+the global <a href="postconf.5.html#qmgr_message_recipient_limit">qmgr_message_recipient_limit</a> and the per transport
+_recipient_limit) if necessary. The minimum value allowed for this
+parameter is 1.
+</p>
+
+
+</DD>
+
+<DT><b><a name="qmqpd_authorized_clients">qmqpd_authorized_clients</a>
+(default: empty)</b></DT><DD>
+
+<p>
+What remote QMQP clients are allowed to connect to the Postfix QMQP
+server port.
+</p>
+
+<p>
+By default, no client is allowed to use the service. This is
+because the QMQP server will relay mail to any destination.
+</p>
+
+<p>
+Specify a list of client patterns. A list pattern specifies a host
+name, a domain name, an internet address, or a network/mask pattern,
+where the mask specifies the number of bits in the network part.
+When a pattern specifies a file name, its contents are substituted
+for the file name; when a pattern is a "<a href="DATABASE_README.html">type:table</a>" table specification,
+table lookup is used instead. </p>
+
+<p>
+Patterns are separated by whitespace and/or commas. In order to
+reverse the result, precede a pattern with an
+exclamation point (!). The form "!/file/name" is supported only
+in Postfix version 2.4 and later.
+</p>
+
+<p> Pattern matching of domain names is controlled by the presence
+or absence of "<a href="postconf.5.html#qmqpd_authorized_clients">qmqpd_authorized_clients</a>" in the
+<a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a> parameter value. </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#qmqpd_authorized_clients">qmqpd_authorized_clients</a> = !192.168.0.1, 192.168.0.0/24
+</pre>
+
+
+</DD>
+
+<DT><b><a name="qmqpd_client_port_logging">qmqpd_client_port_logging</a>
+(default: no)</b></DT><DD>
+
+<p> Enable logging of the remote QMQP client port in addition to
+the hostname and IP address. The logging format is "host[address]:port".
+</p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="qmqpd_error_delay">qmqpd_error_delay</a>
+(default: 1s)</b></DT><DD>
+
+<p>
+How long the Postfix QMQP server will pause before sending a negative
+reply to the remote QMQP client. The purpose is to slow down confused
+or malicious clients.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="qmqpd_timeout">qmqpd_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The time limit for sending or receiving information over the network.
+If a read or write operation blocks for more than $<a href="postconf.5.html#qmqpd_timeout">qmqpd_timeout</a>
+seconds the Postfix QMQP server gives up and disconnects.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="queue_directory">queue_directory</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The location of the Postfix top-level queue directory. This is the
+root directory of Postfix daemon processes that run chrooted.
+</p>
+
+
+</DD>
+
+<DT><b><a name="queue_file_attribute_count_limit">queue_file_attribute_count_limit</a>
+(default: 100)</b></DT><DD>
+
+<p>
+The maximal number of (name=value) attributes that may be stored
+in a Postfix queue file. The limit is enforced by the <a href="cleanup.8.html">cleanup(8)</a>
+server.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="queue_minfree">queue_minfree</a>
+(default: 0)</b></DT><DD>
+
+<p>
+The minimal amount of free space in bytes in the queue file system
+that is needed to receive mail. This is currently used by the
+Postfix SMTP server to decide if it will accept any mail at all.
+</p>
+
+<p>
+By default, the Postfix SMTP server rejects MAIL FROM commands when
+the amount of free space is less than 1.5*$<a href="postconf.5.html#message_size_limit">message_size_limit</a>
+(Postfix version 2.1 and later).
+To specify a higher minimum free space limit, specify a <a href="postconf.5.html#queue_minfree">queue_minfree</a>
+value that is at least 1.5*$<a href="postconf.5.html#message_size_limit">message_size_limit</a>.
+</p>
+
+<p>
+With Postfix versions 2.0 and earlier, a <a href="postconf.5.html#queue_minfree">queue_minfree</a> value of
+zero means there is no minimum required amount of free space.
+</p>
+
+
+</DD>
+
+<DT><b><a name="queue_run_delay">queue_run_delay</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The time between <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> scans by the queue manager;
+prior to Postfix 2.4 the default value was 1000s.
+</p>
+
+<p> This parameter should be set less than or equal to
+$<a href="postconf.5.html#minimal_backoff_time">minimal_backoff_time</a>. See also $<a href="postconf.5.html#maximal_backoff_time">maximal_backoff_time</a>. </p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="queue_service_name">queue_service_name</a>
+(default: qmgr)</b></DT><DD>
+
+<p>
+The name of the <a href="qmgr.8.html">qmgr(8)</a> service. This service manages the Postfix
+queue and schedules delivery requests.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="rbl_reply_maps">rbl_reply_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional lookup tables with RBL response templates. The tables are
+indexed by the RBL domain name. By default, Postfix uses the default
+template as specified with the <a href="postconf.5.html#default_rbl_reply">default_rbl_reply</a> configuration
+parameter. See there for a discussion of the syntax of RBL reply
+templates.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="readme_directory">readme_directory</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+The location of Postfix README files that describe how to build,
+configure or operate a specific Postfix subsystem or feature.
+</p>
+
+
+</DD>
+
+<DT><b><a name="receive_override_options">receive_override_options</a>
+(default: empty)</b></DT><DD>
+
+<p> Enable or disable recipient validation, built-in content
+filtering, or address mapping. Typically, these are specified in
+<a href="master.5.html">master.cf</a> as command-line arguments for the <a href="smtpd.8.html">smtpd(8)</a>, <a href="qmqpd.8.html">qmqpd(8)</a> or
+<a href="pickup.8.html">pickup(8)</a> daemons. </p>
+
+<p> Specify zero or more of the following options. The options
+override <a href="postconf.5.html">main.cf</a> settings and are either implemented by <a href="smtpd.8.html">smtpd(8)</a>,
+<a href="qmqpd.8.html">qmqpd(8)</a>, or <a href="pickup.8.html">pickup(8)</a> themselves, or they are forwarded to the
+cleanup server. </p>
+
+<dl>
+
+<dt><b><a name="no_unknown_recipient_checks">no_unknown_recipient_checks</a></b></dt>
+
+<dd>Do not try to reject unknown recipients (SMTP server only).
+This is typically specified AFTER an external content filter.
+</dd>
+
+<dt><b><a name="no_address_mappings">no_address_mappings</a></b></dt>
+
+<dd>Disable canonical address mapping, virtual alias map expansion,
+address masquerading, and automatic BCC (blind carbon-copy)
+recipients. This is typically specified BEFORE an external content
+filter. </dd>
+
+<dt><b><a name="no_header_body_checks">no_header_body_checks</a></b></dt>
+
+<dd>Disable header/body_checks. This is typically specified AFTER
+an external content filter. </dd>
+
+<dt><b><a name="no_milters">no_milters</a></b></dt>
+
+<dd>Disable Milter (mail filter) applications. This is typically
+specified AFTER an external content filter. </dd>
+
+</dl>
+
+<p>
+Note: when the "BEFORE content filter" <a href="postconf.5.html#receive_override_options">receive_override_options</a>
+setting is specified in the <a href="postconf.5.html">main.cf</a> file, specify the "AFTER content
+filter" <a href="postconf.5.html#receive_override_options">receive_override_options</a> setting in <a href="master.5.html">master.cf</a> (and vice
+versa).
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#receive_override_options">receive_override_options</a> =
+ <a href="postconf.5.html#no_unknown_recipient_checks">no_unknown_recipient_checks</a>, <a href="postconf.5.html#no_header_body_checks">no_header_body_checks</a>
+<a href="postconf.5.html#receive_override_options">receive_override_options</a> = <a href="postconf.5.html#no_address_mappings">no_address_mappings</a>
+</pre>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="recipient_bcc_maps">recipient_bcc_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional BCC (blind carbon-copy) address lookup tables, indexed by
+recipient address. The BCC address (multiple results are not
+supported) is added when mail enters from outside of Postfix.
+</p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p>
+The table search order is as follows:
+</p>
+
+<ul>
+
+<li> Look up the "user+extension@domain.tld" address including the
+optional address extension.
+
+<li> Look up the "user@domain.tld" address without the optional
+address extension.
+
+<li> Look up the "user+extension" address local part when the
+recipient domain equals $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
+or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.
+
+<li> Look up the "user" address local part when the recipient domain
+equals $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.
+
+<li> Look up the "@domain.tld" part.
+
+</ul>
+
+<p>
+Note: with Postfix 2.3 and later the BCC address is added as if it
+was specified with NOTIFY=NONE. The sender will not be notified
+when the BCC address is undeliverable, as long as all down-stream
+software implements <a href="http://tools.ietf.org/html/rfc3461">RFC 3461</a>.
+</p>
+
+<p>
+Note: with Postfix 2.2 and earlier the sender will unconditionally
+be notified when the BCC address is undeliverable.
+</p>
+
+<p> Note: automatic BCC recipients are produced only for new mail.
+To avoid mailer loops, automatic BCC recipients are not generated
+after Postfix forwards mail internally, or after Postfix generates
+mail itself. </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#recipient_bcc_maps">recipient_bcc_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/recipient_bcc
+</pre>
+
+<p>
+After a change, run "<b>postmap /etc/postfix/recipient_bcc</b>".
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="recipient_canonical_classes">recipient_canonical_classes</a>
+(default: envelope_recipient, header_recipient)</b></DT><DD>
+
+<p> What addresses are subject to <a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> address
+mapping. By default, <a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> address mapping is
+applied to envelope recipient addresses, and to header recipient
+addresses. </p>
+
+<p> Specify one or more of: envelope_recipient, header_recipient
+</p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="recipient_canonical_maps">recipient_canonical_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional address mapping lookup tables for envelope and header
+recipient addresses.
+The table format and lookups are documented in <a href="canonical.5.html">canonical(5)</a>.
+</p>
+
+<p>
+Note: $<a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> is processed before $<a href="postconf.5.html#canonical_maps">canonical_maps</a>.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/recipient_canonical
+</pre>
+
+
+</DD>
+
+<DT><b><a name="recipient_delimiter">recipient_delimiter</a>
+(default: empty)</b></DT><DD>
+
+<p> The set of characters that can separate a user name from its
+extension (example: user+foo), or a .forward file name from its
+extension (example: .forward+foo). Basically, the software tries
+user+foo and .forward+foo before trying user and .forward. This
+implementation recognizes one delimiter character and one extension
+per email address or .forward file name. </p>
+
+<p> When the <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> set contains multiple characters
+(Postfix 2.11 and later), a user name or .forward file name is
+separated from its extension by the first character that matches
+the <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> set. </p>
+
+<p> See <a href="canonical.5.html">canonical(5)</a>, <a href="local.8.html">local(8)</a>, <a href="relocated.5.html">relocated(5)</a> and <a href="virtual.5.html">virtual(5)</a> for the
+effects of <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> on lookups in aliases, canonical,
+virtual, and relocated maps, and see the <a href="postconf.5.html#propagate_unmatched_extensions">propagate_unmatched_extensions</a>
+parameter for propagating an extension from one email address to
+another. </p>
+
+<p> When used in <a href="postconf.5.html#command_execution_directory">command_execution_directory</a>, <a href="postconf.5.html#forward_path">forward_path</a>, or
+<a href="postconf.5.html#luser_relay">luser_relay</a>, ${<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>} is replaced with the actual
+recipient delimiter that was found in the recipient email address
+(Postfix 2.11 and later), or it is replaced with the <a href="postconf.5.html">main.cf</a>
+<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> parameter value (Postfix 2.10 and earlier).
+</p>
+
+<p> The <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> is not applied to the mailer-daemon
+address, the postmaster address, or the double-bounce address. With
+the default "<a href="postconf.5.html#owner_request_special">owner_request_special</a> = yes" setting, the <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>
+is also not applied to addresses with the special "owner-" prefix
+or the special "-request" suffix. </p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+# Handle Postfix-style extensions.
+<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> = +
+</pre>
+
+<pre>
+# Handle both Postfix and qmail extensions (Postfix 2.11 and later).
+<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> = +-
+</pre>
+
+<pre>
+# Use .forward for mail without address extension, and for mail with
+# an unrecognized address extension.
+<a href="postconf.5.html#forward_path">forward_path</a> = $home/.forward${<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>}${extension},
+ $home/.forward
+</pre>
+
+
+</DD>
+
+<DT><b><a name="reject_code">reject_code</a>
+(default: 554)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code when a remote SMTP
+client request is rejected by the "reject" restriction.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="reject_tempfail_action">reject_tempfail_action</a>
+(default: <a href="postconf.5.html#defer_if_permit">defer_if_permit</a>)</b></DT><DD>
+
+<p> The Postfix SMTP server's action when a reject-type restriction
+fails due to a temporary error condition. Specify "defer" to defer
+the remote SMTP client request immediately. With the default
+"<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>" action, the Postfix SMTP server continues to look
+for opportunities to reject mail, and defers the client request
+only if it would otherwise be accepted. </p>
+
+<p> For finer control, see: <a href="postconf.5.html#unverified_recipient_tempfail_action">unverified_recipient_tempfail_action</a>,
+<a href="postconf.5.html#unverified_sender_tempfail_action">unverified_sender_tempfail_action</a>, <a href="postconf.5.html#unknown_address_tempfail_action">unknown_address_tempfail_action</a>,
+and <a href="postconf.5.html#unknown_helo_hostname_tempfail_action">unknown_helo_hostname_tempfail_action</a>. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="relay_clientcerts">relay_clientcerts</a>
+(default: empty)</b></DT><DD>
+
+<p> List of tables with remote SMTP client-certificate fingerprints or
+public key fingerprints (Postfix 2.9 and later) for which the Postfix
+SMTP server will allow access with the <a href="postconf.5.html#permit_tls_clientcerts">permit_tls_clientcerts</a>
+feature. The fingerprint digest algorithm is configurable via the
+<a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> parameter (hard-coded as md5 prior to
+Postfix version 2.5). </p>
+
+<p> Postfix lookup tables are in the form of (key, value) pairs.
+Since we only need the key, the value can be chosen freely, e.g.
+the name of the user or host:
+D7:04:2F:A7:0B:8C:A5:21:FA:31:77:E1:41:8A:EE:80 lutzpc.at.home </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#relay_clientcerts">relay_clientcerts</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/relay_clientcerts
+</pre>
+
+<p>For more fine-grained control, use <a href="postconf.5.html#check_ccert_access">check_ccert_access</a> to select
+an appropriate <a href="access.5.html">access(5)</a> policy for each client.
+See <a href="RESTRICTION_CLASS_README.html">RESTRICTION_CLASS_README</a>.</p>
+
+<p> <b>Note:</b> Postfix 2.9.0&ndash;2.9.5 computed the public key
+fingerprint incorrectly. To use public-key fingerprints, upgrade
+to Postfix 2.9.6 or later. </p>
+
+<p>This feature is available with Postfix version 2.2.</p>
+
+
+</DD>
+
+<DT><b><a name="relay_destination_concurrency_limit">relay_destination_concurrency_limit</a>
+(default: $<a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a>)</b></DT><DD>
+
+<p> The maximal number of parallel deliveries to the same destination
+via the relay message delivery transport. This limit is enforced
+by the queue manager. The message delivery transport name is the
+first field in the entry in the <a href="master.5.html">master.cf</a> file. </p>
+
+<p> This feature is available in Postfix 2.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="relay_destination_recipient_limit">relay_destination_recipient_limit</a>
+(default: $<a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a>)</b></DT><DD>
+
+<p> The maximal number of recipients per message for the relay
+message delivery transport. This limit is enforced by the queue
+manager. The message delivery transport name is the first field in
+the entry in the <a href="master.5.html">master.cf</a> file. </p>
+
+<p> Setting this parameter to a value of 1 changes the meaning of
+<a href="postconf.5.html#relay_destination_concurrency_limit">relay_destination_concurrency_limit</a> from concurrency per domain
+into concurrency per recipient. </p>
+
+<p> This feature is available in Postfix 2.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="relay_domains">relay_domains</a>
+(default: Postfix &ge; 3.0: empty, Postfix &lt; 3.0: $<a href="postconf.5.html#mydestination">mydestination</a>)</b></DT><DD>
+
+<p> What destination domains (and subdomains thereof) this system
+will relay mail to. For details about how
+the <a href="postconf.5.html#relay_domains">relay_domains</a> value is used, see the description of the
+<a href="postconf.5.html#permit_auth_destination">permit_auth_destination</a> and <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a> SMTP recipient
+restrictions. </p>
+
+<p> Domains that match $<a href="postconf.5.html#relay_domains">relay_domains</a> are delivered with the
+$<a href="postconf.5.html#relay_transport">relay_transport</a> mail delivery transport. The SMTP server validates
+recipient addresses with $<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> and rejects non-existent
+recipients. See also the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domains</a> address class in the
+<a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> file. </p>
+
+<p> Note: Postfix will not automatically forward mail for domains
+that list this system as their primary or backup MX host. See the
+<a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> restriction in the <a href="postconf.5.html">postconf(5)</a> manual page. </p>
+
+<p> Specify a list of host or domain names, "/file/name" patterns
+or "<a href="DATABASE_README.html">type:table</a>" lookup tables, separated by commas and/or whitespace.
+Continue long lines by starting the next line with whitespace. A
+"/file/name" pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>"
+lookup table is matched when a (parent) domain appears as lookup
+key. Specify "!pattern" to exclude a domain from the list. The form
+"!/file/name" is supported only in Postfix version 2.4 and later.
+</p>
+
+<p> Pattern matching of domain names is controlled by the presence
+or absence of "<a href="postconf.5.html#relay_domains">relay_domains</a>" in the <a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a>
+parameter value. </p>
+
+
+</DD>
+
+<DT><b><a name="relay_domains_reject_code">relay_domains_reject_code</a>
+(default: 554)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code when a client
+request is rejected by the <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a> recipient
+restriction.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="relay_recipient_maps">relay_recipient_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional lookup tables with all valid addresses in the domains
+that match $<a href="postconf.5.html#relay_domains">relay_domains</a>. Specify @domain as a wild-card for
+domains that have no valid recipient list, and become a source of
+backscatter mail: Postfix accepts spam for non-existent recipients
+and then floods innocent people with undeliverable mail. Technically,
+tables
+listed with $<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> are used as lists: Postfix needs
+to know only if a lookup string is found or not, but it does not
+use the result from table lookup. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p>
+If this parameter is non-empty, then the Postfix SMTP server will reject
+mail to unknown relay users. This feature is off by default.
+</p>
+
+<p>
+See also the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domains</a> address class in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a>
+file.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/relay_recipients
+</pre>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="relay_transport">relay_transport</a>
+(default: relay)</b></DT><DD>
+
+<p>
+The default mail delivery transport and next-hop destination for
+remote delivery to domains listed with $<a href="postconf.5.html#relay_domains">relay_domains</a>. In order of
+decreasing precedence, the nexthop destination is taken from
+$<a href="postconf.5.html#relay_transport">relay_transport</a>, $<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>, $<a href="postconf.5.html#relayhost">relayhost</a>, or
+from the recipient domain. This information can be overruled with
+the <a href="transport.5.html">transport(5)</a> table.
+</p>
+
+<p>
+Specify a string of the form <i>transport:nexthop</i>, where <i>transport</i>
+is the name of a mail delivery transport defined in <a href="master.5.html">master.cf</a>.
+The <i>:nexthop</i> destination is optional; its syntax is documented
+in the manual page of the corresponding delivery agent.
+</p>
+
+<p>
+See also the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domains</a> address class in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a>
+file.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="relayhost">relayhost</a>
+(default: empty)</b></DT><DD>
+
+<p>
+The next-hop destination of non-local mail; overrides non-local
+domains in recipient addresses. This information is overruled with
+<a href="postconf.5.html#relay_transport">relay_transport</a>, <a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a>,
+<a href="postconf.5.html#default_transport">default_transport</a>, <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>
+and with the <a href="transport.5.html">transport(5)</a> table.
+</p>
+
+<p>
+On an intranet, specify the organizational domain name. If your
+internal DNS uses no MX records, specify the name of the intranet
+gateway host instead.
+</p>
+
+<p>
+In the case of SMTP, specify a domain name, hostname, hostname:port,
+[hostname]:port, [hostaddress] or [hostaddress]:port. The form
+[hostname] turns off MX lookups.
+</p>
+
+<p>
+If you're connected via UUCP, see the <a href="UUCP_README.html">UUCP_README</a> file for useful
+information.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#relayhost">relayhost</a> = $<a href="postconf.5.html#mydomain">mydomain</a>
+<a href="postconf.5.html#relayhost">relayhost</a> = [gateway.example.com]
+<a href="postconf.5.html#relayhost">relayhost</a> = uucphost
+<a href="postconf.5.html#relayhost">relayhost</a> = [an.ip.add.ress]
+</pre>
+
+
+</DD>
+
+<DT><b><a name="relocated_maps">relocated_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional lookup tables with new contact information for users or
+domains that no longer exist. The table format and lookups are
+documented in <a href="relocated.5.html">relocated(5)</a>.
+</p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p>
+If you use this feature, run "<b>postmap /etc/postfix/relocated</b>" to
+build the necessary DBM or DB file after change, then "<b>postfix
+reload</b>" to make the changes visible.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#relocated_maps">relocated_maps</a> = <a href="DATABASE_README.html#types">dbm</a>:/etc/postfix/relocated
+<a href="postconf.5.html#relocated_maps">relocated_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/relocated
+</pre>
+
+
+</DD>
+
+<DT><b><a name="remote_header_rewrite_domain">remote_header_rewrite_domain</a>
+(default: empty)</b></DT><DD>
+
+<p> Don't rewrite message headers from remote clients at all when
+this parameter is empty; otherwise, rewrite message headers and
+append the specified domain name to incomplete addresses. The
+<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> parameter controls what clients Postfix
+considers local. </p>
+
+<p> Examples: </p>
+
+<p> The safe setting: append "domain.invalid" to incomplete header
+addresses from remote SMTP clients, so that those addresses cannot
+be confused with local addresses. </p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> = domain.invalid
+</pre>
+</blockquote>
+
+<p> The default, purist, setting: don't rewrite headers from remote
+clients at all. </p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> =
+</pre>
+</blockquote>
+
+
+</DD>
+
+<DT><b><a name="require_home_directory">require_home_directory</a>
+(default: no)</b></DT><DD>
+
+<p>
+Require that a <a href="local.8.html">local(8)</a> recipient's home directory exists
+before mail delivery is attempted. By default this test is disabled.
+It can be useful for environments that import home directories to
+the mail server (IMPORTING HOME DIRECTORIES IS NOT RECOMMENDED).
+</p>
+
+
+</DD>
+
+<DT><b><a name="reset_owner_alias">reset_owner_alias</a>
+(default: no)</b></DT><DD>
+
+<p> Reset the <a href="local.8.html">local(8)</a> delivery agent's idea of the owner-alias
+attribute, when delivering mail to a child alias that does not have
+its own owner alias. </p>
+
+<p> This feature is available in Postfix 2.8 and later. With older
+Postfix releases, the behavior is as if this parameter is set to
+"yes". </p>
+
+<p> As documented in <a href="aliases.5.html">aliases(5)</a>, when an alias <i>name</i> has a
+companion alias named owner-<i>name</i>, this will replace the
+envelope sender address, so that delivery errors will be
+reported to the owner alias instead of the sender. This configuration
+is recommended for mailing lists. <p>
+
+<p> A less known property of the owner alias is that it also forces
+the <a href="local.8.html">local(8)</a> delivery agent to write local and remote addresses
+from alias expansion to a new queue file, instead of attempting to
+deliver mail to local addresses as soon as they come out of alias
+expansion. </p>
+
+<p> Writing local addresses from alias expansion to a new queue
+file allows for robust handling of temporary delivery errors: errors
+with one local member have no effect on deliveries to other members
+of the list. On the other hand, delivery to local addresses as
+soon as they come out of alias expansion is fragile: a temporary
+error with one local address from alias expansion will cause the
+entire alias to be expanded repeatedly until the error goes away,
+or until the message expires in the queue. In that case, a problem
+with one list member results in multiple message deliveries to other
+list members. </p>
+
+<p> The default behavior of Postfix 2.8 and later is to keep the
+owner-alias attribute of the parent alias, when delivering mail to
+a child alias that does not have its own owner alias. Then, local
+addresses from that child alias will be written to a new queue file,
+and a temporary error with one local address will not affect delivery
+to other mailing list members. </p>
+
+<p> Unfortunately, older Postfix releases reset the owner-alias
+attribute when delivering mail to a child alias that does not have
+its own owner alias. To be precise, this resets only the decision
+to create a new queue file, not the decision to override the envelope
+sender address. The <a href="local.8.html">local(8)</a> delivery agent then attempts to
+deliver local addresses as soon as they come out of child alias
+expansion. If delivery to any address from child alias expansion
+fails with a temporary error condition, the entire mailing list may
+be expanded repeatedly until the mail expires in the queue, resulting
+in multiple deliveries of the same message to mailing list members.
+</p>
+
+
+</DD>
+
+<DT><b><a name="resolve_dequoted_address">resolve_dequoted_address</a>
+(default: yes)</b></DT><DD>
+
+<p> Resolve a recipient address safely instead of correctly, by
+looking inside quotes. </p>
+
+<p> By default, the Postfix address resolver does not quote the
+address localpart as per <a href="http://tools.ietf.org/html/rfc822">RFC 822</a>, so that additional @ or % or !
+operators remain visible. This behavior is safe but it is also
+technically incorrect. </p>
+
+<p> If you specify "<a href="postconf.5.html#resolve_dequoted_address">resolve_dequoted_address</a> = no", then
+the Postfix
+resolver will not know about additional @ etc. operators in the
+address localpart. This opens opportunities for obscure mail relay
+attacks with user@domain@domain addresses when Postfix provides
+backup MX service for Sendmail systems. </p>
+
+
+</DD>
+
+<DT><b><a name="resolve_null_domain">resolve_null_domain</a>
+(default: no)</b></DT><DD>
+
+<p> Resolve an address that ends in the "@" null domain as if the
+local hostname were specified, instead of rejecting the address as
+invalid. </p>
+
+<p> This feature is available in Postfix 2.1 and later.
+Earlier versions always resolve the null domain as the local
+hostname. </p>
+
+<p> The Postfix SMTP server uses this feature to reject mail from
+or to addresses that end in the "@" null domain, and from addresses
+that rewrite into a form that ends in the "@" null domain. </p>
+
+
+</DD>
+
+<DT><b><a name="resolve_numeric_domain">resolve_numeric_domain</a>
+(default: no)</b></DT><DD>
+
+<p> Resolve "user@ipaddress" as "user@[ipaddress]", instead of
+rejecting the address as invalid. </p>
+
+<p> This feature is available in Postfix 2.3 and later.
+
+
+</DD>
+
+<DT><b><a name="rewrite_service_name">rewrite_service_name</a>
+(default: rewrite)</b></DT><DD>
+
+<p>
+The name of the address rewriting service. This service rewrites
+addresses to standard form and resolves them to a (delivery method,
+next-hop host, recipient) triple.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="sample_directory">sample_directory</a>
+(default: /etc/postfix)</b></DT><DD>
+
+<p>
+The name of the directory with example Postfix configuration files.
+Starting with Postfix 2.1, these files have been replaced with the
+<a href="postconf.5.html">postconf(5)</a> manual page.
+</p>
+
+
+</DD>
+
+<DT><b><a name="send_cyrus_sasl_authzid">send_cyrus_sasl_authzid</a>
+(default: no)</b></DT><DD>
+
+<p> When authenticating to a remote SMTP or LMTP server with the
+default setting "no", send no SASL authoriZation ID (authzid); send
+only the SASL authentiCation ID (authcid) plus the authcid's password.
+</p>
+
+<p> The non-default setting "yes" enables the behavior of older
+Postfix versions. These always send a SASL authzid that is equal
+to the SASL authcid, but this causes interoperability problems
+with some SMTP servers. </p>
+
+<p> This feature is available in Postfix 2.4.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="sender_based_routing">sender_based_routing</a>
+(default: no)</b></DT><DD>
+
+<p>
+This parameter should not be used. It was replaced by <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>
+in Postfix version 2.3.
+</p>
+
+
+</DD>
+
+<DT><b><a name="sender_bcc_maps">sender_bcc_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional BCC (blind carbon-copy) address lookup tables, indexed
+by sender address. The BCC address (multiple results are not
+supported) is added when mail enters from outside of Postfix. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p>
+The table search order is as follows:
+</p>
+
+<ul>
+
+<li> Look up the "user+extension@domain.tld" address including the
+optional address extension.
+
+<li> Look up the "user@domain.tld" address without the optional
+address extension.
+
+<li> Look up the "user+extension" address local part when the
+sender domain equals $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
+or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.
+
+<li> Look up the "user" address local part when the sender domain
+equals $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.
+
+<li> Look up the "@domain.tld" part.
+
+</ul>
+
+<p>
+Note: with Postfix 2.3 and later the BCC address is added as if it
+was specified with NOTIFY=NONE. The sender will not be notified
+when the BCC address is undeliverable, as long as all down-stream
+software implements <a href="http://tools.ietf.org/html/rfc3461">RFC 3461</a>.
+</p>
+
+<p>
+Note: with Postfix 2.2 and earlier the sender will be notified
+when the BCC address is undeliverable.
+</p>
+
+<p> Note: automatic BCC recipients are produced only for new mail.
+To avoid mailer loops, automatic BCC recipients are not generated
+after Postfix forwards mail internally, or after Postfix generates
+mail itself. </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#sender_bcc_maps">sender_bcc_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/sender_bcc
+</pre>
+
+<p>
+After a change, run "<b>postmap /etc/postfix/sender_bcc</b>".
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="sender_canonical_classes">sender_canonical_classes</a>
+(default: envelope_sender, header_sender)</b></DT><DD>
+
+<p> What addresses are subject to <a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> address
+mapping. By default, <a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> address mapping is
+applied to envelope sender addresses, and to header sender addresses.
+</p>
+
+<p> Specify one or more of: envelope_sender, header_sender </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="sender_canonical_maps">sender_canonical_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional address mapping lookup tables for envelope and header
+sender addresses.
+The table format and lookups are documented in <a href="canonical.5.html">canonical(5)</a>.
+</p>
+
+<p>
+Example: you want to rewrite the SENDER address "user@ugly.domain"
+to "user@pretty.domain", while still being able to send mail to
+the RECIPIENT address "user@ugly.domain".
+</p>
+
+<p>
+Note: $<a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> is processed before $<a href="postconf.5.html#canonical_maps">canonical_maps</a>.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/sender_canonical
+</pre>
+
+
+</DD>
+
+<DT><b><a name="sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> A sender-dependent override for the global <a href="postconf.5.html#default_transport">default_transport</a>
+parameter setting. The tables are searched by the envelope sender
+address and @domain. A lookup result of DUNNO terminates the search
+without overriding the global <a href="postconf.5.html#default_transport">default_transport</a> parameter setting.
+This information is overruled with the <a href="transport.5.html">transport(5)</a> table. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p> Note: this overrides <a href="postconf.5.html#default_transport">default_transport</a>, not <a href="postconf.5.html#transport_maps">transport_maps</a>, and
+therefore the expected syntax is that of <a href="postconf.5.html#default_transport">default_transport</a>, not the
+syntax of <a href="postconf.5.html#transport_maps">transport_maps</a>. Specifically, this does not support the
+<a href="postconf.5.html#transport_maps">transport_maps</a> syntax for null transport, null nexthop, or null
+email addresses. </p>
+
+<p> For safety reasons, this feature does not allow $number
+substitutions in regular expression maps. </p>
+
+<p> This feature is available in Postfix 2.7 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> A sender-dependent override for the global <a href="postconf.5.html#relayhost">relayhost</a> parameter
+setting. The tables are searched by the envelope sender address and
+@domain. A lookup result of DUNNO terminates the search without
+overriding the global <a href="postconf.5.html#relayhost">relayhost</a> parameter setting (Postfix 2.6 and
+later). This information is overruled with <a href="postconf.5.html#relay_transport">relay_transport</a>,
+<a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a>, <a href="postconf.5.html#default_transport">default_transport</a> and with
+the <a href="transport.5.html">transport(5)</a> table. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p> For safety reasons, this feature does not allow $number
+substitutions in regular expression maps. </p>
+
+<p>
+This feature is available in Postfix 2.3 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="sendmail_fix_line_endings">sendmail_fix_line_endings</a>
+(default: always)</b></DT><DD>
+
+<p> Controls how the Postfix sendmail command converts email message
+line endings from &lt;CR&gt;&lt;LF&gt; into UNIX format (&lt;LF&gt;).
+</p>
+
+<dl>
+
+<dt> <b>always</b> </dt> <dd> Always convert message lines ending
+in &lt;CR&gt;&lt;LF&gt;. This setting is the default with Postfix
+2.9 and later. </dd>
+
+<dt> <b>strict</b> </dt> <dd> Convert message lines ending in
+&lt;CR&gt;&lt;LF&gt; only if the first input line ends in
+&lt;CR&gt;&lt;LF&gt;. This setting is backwards-compatible with
+Postfix 2.8 and earlier. </dd>
+
+<dt> <b>never</b> </dt> <dd> Never convert message lines ending in
+&lt;CR&gt;&lt;LF&gt;. This setting exists for completeness only.
+</dd>
+
+</dl>
+
+<p> This feature is available in Postfix 2.9 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="sendmail_path">sendmail_path</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+A Sendmail compatibility feature that specifies the location of
+the Postfix <a href="sendmail.1.html">sendmail(1)</a> command. This command can be used to
+submit mail into the Postfix queue.
+</p>
+
+
+</DD>
+
+<DT><b><a name="service_name">service_name</a>
+(read-only)</b></DT><DD>
+
+<p> The <a href="master.5.html">master.cf</a> service name of a Postfix daemon process. This
+can be used to distinguish the logging from different services that
+use the same program name. </p>
+
+<p> Example <a href="master.5.html">master.cf</a> entries: </p>
+
+<pre>
+# Distinguish inbound MTA logging from submission and smtps logging.
+smtp inet n - n - - smtpd
+submission inet n - n - - smtpd
+ -o <a href="postconf.5.html#syslog_name">syslog_name</a>=postfix/$<a href="postconf.5.html#service_name">service_name</a>
+smtps inet n - n - - smtpd
+ -o <a href="postconf.5.html#syslog_name">syslog_name</a>=postfix/$<a href="postconf.5.html#service_name">service_name</a>
+</pre>
+
+<pre>
+# Distinguish outbound MTA logging from inbound relay logging.
+smtp unix - - n - - smtp
+relay unix - - n - - smtp
+ -o <a href="postconf.5.html#syslog_name">syslog_name</a>=postfix/$<a href="postconf.5.html#service_name">service_name</a>
+</pre>
+
+
+</DD>
+
+<DT><b><a name="service_throttle_time">service_throttle_time</a>
+(default: 60s)</b></DT><DD>
+
+<p>
+How long the Postfix <a href="master.8.html">master(8)</a> waits before forking a server that
+appears to be malfunctioning.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="setgid_group">setgid_group</a>
+(default: postdrop)</b></DT><DD>
+
+<p>
+The group ownership of set-gid Postfix commands and of group-writable
+Postfix directories. When this parameter value is changed you need
+to re-run "<b>postfix set-permissions</b>" (with Postfix version 2.0 and
+earlier: "<b>/etc/postfix/post-install set-permissions</b>".
+</p>
+
+
+</DD>
+
+<DT><b><a name="shlib_directory">shlib_directory</a>
+(default: see 'postconf -d' output)</b></DT><DD>
+
+<p> The location of Postfix dynamically-linked libraries
+(libpostfix-*.so), and the default location of Postfix database
+plugins (postfix-*.so) that have a relative pathname in the
+dynamicmaps.cf file. The <a href="postconf.5.html#shlib_directory">shlib_directory</a> parameter defaults to
+"no" when Postfix dynamically-linked libraries and database plugins
+are disabled at compile time, otherwise it typically defaults to
+/usr/lib/postfix or /usr/local/lib/postfix. </p>
+
+<p> Notes: </p>
+
+<ul>
+
+<li> <p> The directory specified with <a href="postconf.5.html#shlib_directory">shlib_directory</a> should contain
+only Postfix-related files. Postfix dynamically-linked libraries
+and database plugins should not be installed in a "public" system
+directory such as /usr/lib or /usr/local/lib. Linking Postfix
+dynamically-linked library files or database plugins into non-Postfix
+programs is not supported. Postfix dynamically-linked libraries
+and database plugins implement a Postfix-internal API that changes
+without maintaining compatibility. </p>
+
+<li> <p> You can change the <a href="postconf.5.html#shlib_directory">shlib_directory</a> value after Postfix is
+built. However, you may have to run ldconfig or equivalent to prevent
+Postfix programs from failing because the libpostfix-*.so files are
+not found. No ldconfig command is needed if you keep the libpostfix-*.so
+files in the compiled-in default $<a href="postconf.5.html#shlib_directory">shlib_directory</a> location. </p>
+
+</ul>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="show_user_unknown_table_name">show_user_unknown_table_name</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Display the name of the recipient table in the "User unknown"
+responses. The extra detail makes troubleshooting easier but also
+reveals information that is nobody else's business.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="showq_service_name">showq_service_name</a>
+(default: showq)</b></DT><DD>
+
+<p>
+The name of the <a href="showq.8.html">showq(8)</a> service. This service produces mail queue
+status reports.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_address_preference">smtp_address_preference</a>
+(default: any)</b></DT><DD>
+
+<p> The address type ("ipv6", "ipv4" or "any") that the Postfix
+SMTP client will try first, when a destination has IPv6 and IPv4
+addresses with equal MX preference. This feature has no effect
+unless the <a href="postconf.5.html#inet_protocols">inet_protocols</a> setting enables both IPv4 and IPv6. </p>
+
+<p> Postfix SMTP client address preference has evolved. With Postfix
+2.8 the default is "ipv6"; earlier implementations are hard-coded
+to prefer IPv6 over IPv4. </p>
+
+<p> Notes for mail delivery between sites that have both IPv4 and
+IPv6 connectivity: </p>
+
+<ul>
+
+<li> <p> The setting "<a href="postconf.5.html#smtp_address_preference">smtp_address_preference</a> = ipv6" is unsafe.
+It can fail to deliver mail when there is an outage that affects
+IPv6, while the destination is still reachable over IPv4. </p>
+
+<li> <p> The setting "<a href="postconf.5.html#smtp_address_preference">smtp_address_preference</a> = any" is safe. With
+this, mail will eventually be delivered even if there is an outage
+that affects IPv6 or IPv4, as long as it does not affect both. </p>
+
+</ul>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_address_verify_target">smtp_address_verify_target</a>
+(default: rcpt)</b></DT><DD>
+
+<p> In the context of email address verification, the SMTP protocol
+stage that determines whether an email address is deliverable.
+Specify one of "rcpt" or "data". The latter is needed with remote
+SMTP servers that reject recipients after the DATA command. Use
+<a href="postconf.5.html#transport_maps">transport_maps</a> to apply this feature selectively: </p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#transport_maps">transport_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/transport
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/transport:
+ smtp-domain-that-verifies-after-data smtp-data-target:
+ lmtp-domain-that-verifies-after-data lmtp-data-target:
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="master.5.html">master.cf</a>:
+ smtp-data-target unix - - n - - smtp
+ -o <a href="postconf.5.html#smtp_address_verify_target">smtp_address_verify_target</a>=data
+ lmtp-data-target unix - - n - - lmtp
+ -o <a href="postconf.5.html#lmtp_address_verify_target">lmtp_address_verify_target</a>=data
+</pre>
+</blockquote>
+
+<p> Unselective use of the "data" target does no harm, but will
+result in unnecessary "lost connection after DATA" events at remote
+SMTP/LMTP servers. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_always_send_ehlo">smtp_always_send_ehlo</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Always send EHLO at the start of an SMTP session.
+</p>
+
+<p>
+With "<a href="postconf.5.html#smtp_always_send_ehlo">smtp_always_send_ehlo</a> = no", the Postfix SMTP client sends
+EHLO only when
+the word "ESMTP" appears in the server greeting banner (example:
+220 spike.porcupine.org ESMTP Postfix).
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_balance_inet_protocols">smtp_balance_inet_protocols</a>
+(default: yes)</b></DT><DD>
+
+<p> When a remote destination resolves to a combination of IPv4 and
+IPv6 addresses, ensure that the Postfix SMTP client can try both
+address types before it runs into the <a href="postconf.5.html#smtp_mx_address_limit">smtp_mx_address_limit</a>. </p>
+
+<p> This avoids an interoperability problem when a destination resolves
+to primarily IPv6 addresses, the smtp_address_limit feature eliminates
+most or all IPv4 addresses, and the destination is not reachable over
+IPv6. </p>
+
+<p> This feature is available in Postfix 3.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_bind_address">smtp_bind_address</a>
+(default: empty)</b></DT><DD>
+
+<p>
+An optional numerical network address that the Postfix SMTP client
+should bind to when making an IPv4 connection.
+</p>
+
+<p>
+This can be specified in the <a href="postconf.5.html">main.cf</a> file for all SMTP clients, or
+it can be specified in the <a href="master.5.html">master.cf</a> file for a specific client,
+for example:
+</p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="master.5.html">master.cf</a>:
+ smtp ... smtp -o <a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a>=11.22.33.44
+</pre>
+</blockquote>
+
+<p> Note 1: when <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> specifies no more than one IPv4
+address, and that address is a non-loopback address, it is
+automatically used as the <a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a>. This supports virtual
+IP hosting, but can be a problem on multi-homed firewalls. See the
+<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> documentation for more detail. </p>
+
+<p> Note 2: address information may be enclosed inside <tt>[]</tt>,
+but this form is not required here. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_bind_address6">smtp_bind_address6</a>
+(default: empty)</b></DT><DD>
+
+<p>
+An optional numerical network address that the Postfix SMTP client
+should bind to when making an IPv6 connection.
+</p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+<p>
+This can be specified in the <a href="postconf.5.html">main.cf</a> file for all SMTP clients, or
+it can be specified in the <a href="master.5.html">master.cf</a> file for a specific client,
+for example:
+</p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="master.5.html">master.cf</a>:
+ smtp ... smtp -o <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a>=1:2:3:4:5:6:7:8
+</pre>
+</blockquote>
+
+<p> Note 1: when <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> specifies no more than one IPv6
+address, and that address is a non-loopback address, it is
+automatically used as the <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a>. This supports virtual
+IP hosting, but can be a problem on multi-homed firewalls. See the
+<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> documentation for more detail. </p>
+
+<p> Note 2: address information may be enclosed inside <tt>[]</tt>,
+but this form is not recommended here. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_body_checks">smtp_body_checks</a>
+(default: empty)</b></DT><DD>
+
+<p> Restricted <a href="header_checks.5.html">body_checks(5)</a> tables for the Postfix SMTP client.
+These tables are searched while mail is being delivered. Actions
+that change the delivery time or destination are not available.
+</p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_cname_overrides_servername">smtp_cname_overrides_servername</a>
+(default: version dependent)</b></DT><DD>
+
+<p> When the remote SMTP servername is a DNS CNAME, replace the
+servername with the result from CNAME expansion for the purpose of
+logging, SASL password lookup, TLS
+policy decisions, or TLS certificate verification. The value "no"
+hardens Postfix <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> hostname-based policies against
+false hostname information in DNS CNAME records, and makes SASL
+password file lookups more predictable. This is the default setting
+as of Postfix 2.3. </p>
+
+<p> When DNS CNAME records are validated with secure DNS lookups
+(<a href="postconf.5.html#smtp_dns_support_level">smtp_dns_support_level</a> = dnssec), they are always allowed to
+override the above servername (Postfix 2.11 and later). </p>
+
+<p> This feature is available in Postfix 2.2.9 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_connect_timeout">smtp_connect_timeout</a>
+(default: 30s)</b></DT><DD>
+
+<p>
+The Postfix SMTP client time limit for completing a TCP connection, or
+zero (use the operating system built-in time limit).
+</p>
+
+<p>
+When no connection can be made within the deadline, the Postfix
+SMTP client
+tries the next address on the mail exchanger list. Specify 0 to
+disable the time limit (i.e. use whatever timeout is implemented by
+the operating system).
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_connection_cache_destinations">smtp_connection_cache_destinations</a>
+(default: empty)</b></DT><DD>
+
+<p> Permanently enable SMTP connection caching for the specified
+destinations. With SMTP connection caching, a connection is not
+closed immediately after completion of a mail transaction. Instead,
+the connection is kept open for up to $<a href="postconf.5.html#smtp_connection_cache_time_limit">smtp_connection_cache_time_limit</a>
+seconds. This allows connections to be reused for other deliveries,
+and can improve mail delivery performance. </p>
+
+<p> Specify a comma or white space separated list of destinations
+or pseudo-destinations: </p>
+
+<ul>
+
+<li> if mail is sent without a <a href="postconf.5.html#relayhost">relay host</a>: a domain name (the
+right-hand side of an email address, without the [] around a numeric
+IP address),
+
+<li> if mail is sent via a <a href="postconf.5.html#relayhost">relay host</a>: a <a href="postconf.5.html#relayhost">relay host</a> name (without
+[] or non-default TCP port), as specified in <a href="postconf.5.html">main.cf</a> or in the
+transport map,
+
+<li> if mail is sent via a UNIX-domain socket: a pathname (without
+the unix: prefix),
+
+<li> a /file/name with domain names and/or <a href="postconf.5.html#relayhost">relay host</a> names as
+defined above,
+
+<li> a "<a href="DATABASE_README.html">type:table</a>" with domain names and/or <a href="postconf.5.html#relayhost">relay host</a> names on
+the left-hand side. The right-hand side result from "<a href="DATABASE_README.html">type:table</a>"
+lookups is ignored.
+
+</ul>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_connection_cache_on_demand">smtp_connection_cache_on_demand</a>
+(default: yes)</b></DT><DD>
+
+<p> Temporarily enable SMTP connection caching while a destination
+has a high volume of mail in the <a href="QSHAPE_README.html#active_queue">active queue</a>. With SMTP connection
+caching, a connection is not closed immediately after completion
+of a mail transaction. Instead, the connection is kept open for
+up to $<a href="postconf.5.html#smtp_connection_cache_time_limit">smtp_connection_cache_time_limit</a> seconds. This allows
+connections to be reused for other deliveries, and can improve mail
+delivery performance. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_connection_cache_time_limit">smtp_connection_cache_time_limit</a>
+(default: 2s)</b></DT><DD>
+
+<p> When SMTP connection caching is enabled, the amount of time that
+an unused SMTP client socket is kept open before it is closed. Do
+not specify larger values without permission from the remote sites.
+</p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_connection_reuse_count_limit">smtp_connection_reuse_count_limit</a>
+(default: 0)</b></DT><DD>
+
+<p> When SMTP connection caching is enabled, the number of times
+that an SMTP session may be reused before it is closed, or zero (no
+limit). With a reuse count limit of N, a connection is used up to
+N+1 times. </p>
+
+<p> NOTE: This feature is unsafe. When a high-volume destination
+has multiple inbound MTAs, then the slowest inbound MTA will attract
+the most connections to that destination. This limitation does not
+exist with the <a href="postconf.5.html#smtp_connection_reuse_time_limit">smtp_connection_reuse_time_limit</a> feature. </p>
+
+<p> This feature is available in Postfix 2.11. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_connection_reuse_time_limit">smtp_connection_reuse_time_limit</a>
+(default: 300s)</b></DT><DD>
+
+<p> The amount of time during which Postfix will use an SMTP
+connection repeatedly. The timer starts when the connection is
+initiated (i.e. it includes the connect, greeting and helo latency,
+in addition to the latencies of subsequent mail delivery transactions).
+</p>
+
+<p> This feature addresses a performance stability problem with
+remote SMTP servers. This problem is not specific to Postfix: it
+can happen when any MTA sends large amounts of SMTP email to a site
+that has multiple MX hosts. </p>
+
+<p> The problem starts when one of a set of MX hosts becomes slower
+than the rest. Even though SMTP clients connect to fast and slow
+MX hosts with equal probability, the slow MX host ends up with more
+simultaneous inbound connections than the faster MX hosts, because
+the slow MX host needs more time to serve each client request. </p>
+
+<p> The slow MX host becomes a connection attractor. If one MX
+host becomes N times slower than the rest, it dominates mail delivery
+latency unless there are more than N fast MX hosts to counter the
+effect. And if the number of MX hosts is smaller than N, the mail
+delivery latency becomes effectively that of the slowest MX host
+divided by the total number of MX hosts. </p>
+
+<p> The solution uses connection caching in a way that differs from
+Postfix version 2.2. By limiting the amount of time during which a connection
+can be used repeatedly (instead of limiting the number of deliveries
+over that connection), Postfix not only restores fairness in the
+distribution of simultaneous connections across a set of MX hosts,
+it also favors deliveries over connections that perform well, which
+is exactly what we want. </p>
+
+<p> The default reuse time limit, 300s, is comparable to the various
+smtp transaction timeouts which are fair estimates of maximum excess
+latency for a slow delivery. Note that hosts may accept thousands
+of messages over a single connection within the default connection
+reuse time limit. This number is much larger than the default Postfix
+version 2.2 limit of 10 messages per cached connection. It may prove necessary
+to lower the limit to avoid interoperability issues with MTAs that
+exhibit bugs when many messages are delivered via a single connection.
+A lower reuse time limit risks losing the benefit of connection
+reuse when the average connection and mail delivery latency exceeds
+the reuse time limit. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_data_done_timeout">smtp_data_done_timeout</a>
+(default: 600s)</b></DT><DD>
+
+<p>
+The Postfix SMTP client time limit for sending the SMTP ".", and
+for receiving the remote SMTP server response.
+</p>
+
+<p>
+When no response is received within the deadline, a warning is
+logged that the mail may be delivered multiple times.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_data_init_timeout">smtp_data_init_timeout</a>
+(default: 120s)</b></DT><DD>
+
+<p>
+The Postfix SMTP client time limit for sending the SMTP DATA command,
+and for receiving the remote SMTP server response.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_data_xfer_timeout">smtp_data_xfer_timeout</a>
+(default: 180s)</b></DT><DD>
+
+<p>
+The Postfix SMTP client time limit for sending the SMTP message content.
+When the connection makes no progress for more than $<a href="postconf.5.html#smtp_data_xfer_timeout">smtp_data_xfer_timeout</a>
+seconds the Postfix SMTP client terminates the transfer.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_defer_if_no_mx_address_found">smtp_defer_if_no_mx_address_found</a>
+(default: no)</b></DT><DD>
+
+<p>
+Defer mail delivery when no MX record resolves to an IP address.
+</p>
+
+<p>
+The default (no) is to return the mail as undeliverable. With older
+Postfix versions the default was to keep trying to deliver the mail
+until someone fixed the MX record or until the mail was too old.
+</p>
+
+<p>
+Note: the Postfix SMTP client always ignores MX records with equal
+or worse preference
+than the local MTA itself.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_delivery_status_filter">smtp_delivery_status_filter</a>
+(default: $<a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a>)</b></DT><DD>
+
+<p> Optional filter for the <a href="smtp.8.html">smtp(8)</a> delivery agent to change the
+delivery status code or explanatory text of successful or unsuccessful
+deliveries. See <a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a> for details. </p>
+
+<p> NOTE: This feature modifies Postfix SMTP client error or non-error
+messages that may or may not be derived from remote SMTP server
+responses. In contrast, the <a href="postconf.5.html#smtp_reply_filter">smtp_reply_filter</a> feature modifies
+remote SMTP server responses only. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_destination_concurrency_limit">smtp_destination_concurrency_limit</a>
+(default: $<a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a>)</b></DT><DD>
+
+<p> The maximal number of parallel deliveries to the same destination
+via the smtp message delivery transport. This limit is enforced by
+the queue manager. The message delivery transport name is the first
+field in the entry in the <a href="master.5.html">master.cf</a> file. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_destination_recipient_limit">smtp_destination_recipient_limit</a>
+(default: $<a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a>)</b></DT><DD>
+
+<p> The maximal number of recipients per message for the smtp
+message delivery transport. This limit is enforced by the queue
+manager. The message delivery transport name is the first field in
+the entry in the <a href="master.5.html">master.cf</a> file. </p>
+
+<p> Setting this parameter to a value of 1 changes the meaning of
+<a href="postconf.5.html#smtp_destination_concurrency_limit">smtp_destination_concurrency_limit</a> from concurrency per domain
+into concurrency per recipient. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_discard_ehlo_keyword_address_maps">smtp_discard_ehlo_keyword_address_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Lookup tables, indexed by the remote SMTP server address, with
+case insensitive lists of EHLO keywords (pipelining, starttls, auth,
+etc.) that the Postfix SMTP client will ignore in the EHLO response from a
+remote SMTP server. See <a href="postconf.5.html#smtp_discard_ehlo_keywords">smtp_discard_ehlo_keywords</a> for details. The
+table is not indexed by hostname for consistency with
+<a href="postconf.5.html#smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a>. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_discard_ehlo_keywords">smtp_discard_ehlo_keywords</a>
+(default: empty)</b></DT><DD>
+
+<p> A case insensitive list of EHLO keywords (pipelining, starttls,
+auth, etc.) that the Postfix SMTP client will ignore in the EHLO
+response from a remote SMTP server. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+<p> Notes: </p>
+
+<ul>
+
+<li> <p> Specify the <b>silent-discard</b> pseudo keyword to prevent
+this action from being logged. </p>
+
+<li> <p> Use the <a href="postconf.5.html#smtp_discard_ehlo_keyword_address_maps">smtp_discard_ehlo_keyword_address_maps</a> feature to
+discard EHLO keywords selectively. </p>
+
+</ul>
+
+
+</DD>
+
+<DT><b><a name="smtp_dns_reply_filter">smtp_dns_reply_filter</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional filter for Postfix SMTP client DNS lookup results.
+Specify zero or more lookup tables. The lookup tables are searched
+in the given order for a match with the DNS lookup result, converted
+to the following form: </p>
+
+<pre>
+ <i>name ttl class type preference value</i>
+</pre>
+
+<p> The <i>class</i> field is always "IN", the <i>preference</i>
+field exists only for MX records, the names of hosts, domains, etc.
+end in ".", and those names are in ASCII form (xn--mumble form in
+the case of UTF8 names). </p>
+
+<p> When a match is found, the table lookup result specifies an
+action. By default, the table query and the action name are
+case-insensitive. Currently, only the <b>IGNORE</b> action is
+implemented. </p>
+
+<p> Notes: </p>
+
+<ul>
+
+<li> <p> Postfix DNS reply filters have no effect on implicit DNS
+lookups through nsswitch.conf or equivalent mechanisms. </p>
+
+<li> <p> The Postfix SMTP/LMTP client uses <a href="postconf.5.html#smtp_dns_reply_filter">smtp_dns_reply_filter</a>
+and <a href="postconf.5.html#lmtp_dns_reply_filter">lmtp_dns_reply_filter</a> only to discover a remote SMTP or LMTP
+service (record types MX, A, AAAAA, and TLSA). These lookups are
+also made to implement the features <a href="postconf.5.html#reject_unverified_sender">reject_unverified_sender</a> and
+<a href="postconf.5.html#reject_unverified_recipient">reject_unverified_recipient</a>. </p>
+
+<li> <p> The Postfix SMTP/LMTP client defers mail delivery when
+a filter removes all lookup results from a successful query. </p>
+
+<li> <p> Postfix SMTP server uses <a href="postconf.5.html#smtpd_dns_reply_filter">smtpd_dns_reply_filter</a> only to
+look up MX, A, AAAAA, and TXT records to implement the features
+<a href="postconf.5.html#reject_unknown_helo_hostname">reject_unknown_helo_hostname</a>, <a href="postconf.5.html#reject_unknown_sender_domain">reject_unknown_sender_domain</a>,
+<a href="postconf.5.html#reject_unknown_recipient_domain">reject_unknown_recipient_domain</a>, reject_rbl_*, and reject_rhsbl_*.
+</p>
+
+<li> <p> The Postfix SMTP server logs a warning or defers mail
+delivery when a filter removes all lookup results from a successful
+query. </p>
+
+</ul>
+
+<p> Example: ignore Google AAAA records in Postfix SMTP client DNS
+lookups, because Google sometimes hard-rejects mail from IPv6 clients
+with valid PTR etc. records. </p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtp_dns_reply_filter">smtp_dns_reply_filter</a> = <a href="pcre_table.5.html">pcre</a>:/etc/postfix/smtp_dns_reply_filter
+</pre>
+
+<pre>
+/etc/postfix/smtp_dns_reply_filter:
+ # /domain ttl IN AAAA address/ action, all case-insensitive.
+ # Note: the domain name ends in ".".
+ /^\S+\.google\.com\.\s+\S+\s+\S+\s+AAAA\s+/ IGNORE
+</pre>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_dns_resolver_options">smtp_dns_resolver_options</a>
+(default: empty)</b></DT><DD>
+
+<p> DNS Resolver options for the Postfix SMTP client. Specify zero
+or more of the following options, separated by comma or whitespace.
+Option names are case-sensitive. Some options refer to domain names
+that are specified in the file /etc/resolv.conf or equivalent. </p>
+
+<dl>
+
+<dt><b>res_defnames</b></dt>
+
+<dd> Append the current domain name to single-component names (those
+that do not contain a "." character). This can produce incorrect
+results, and is the hard-coded behavior prior to Postfix 2.8. </dd>
+
+<dt><b>res_dnsrch</b></dt>
+
+<dd> Search for host names in the current domain and in parent
+domains. This can produce incorrect results and is therefore not
+recommended. </dd>
+
+</dl>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_dns_support_level">smtp_dns_support_level</a>
+(default: empty)</b></DT><DD>
+
+<p> Level of DNS support in the Postfix SMTP client. With
+"<a href="postconf.5.html#smtp_dns_support_level">smtp_dns_support_level</a>" left at its empty default value, the legacy
+"<a href="postconf.5.html#disable_dns_lookups">disable_dns_lookups</a>" parameter controls whether DNS is enabled in
+the Postfix SMTP client, otherwise the legacy parameter is ignored.
+</p>
+
+<p> Specify one of the following: </p>
+
+<dl>
+
+<dt><b>disabled</b></dt>
+
+<dd>Disable DNS lookups. No MX lookups are performed and hostname
+to address lookups are unconditionally "native". This setting is
+not appropriate for hosts that deliver mail to the public Internet.
+Some obsolete how-to documents recommend disabling DNS lookups in
+some configurations with content_filters. This is no longer required
+and strongly discouraged. </dd>
+
+<dt><b>enabled</b></dt>
+
+<dd>Enable DNS lookups. Nexthop destination domains not enclosed
+in "[]" will be subject to MX lookups. If "dns" and "native" are
+included in the "<a href="postconf.5.html#smtp_host_lookup">smtp_host_lookup</a>" parameter value, DNS will be
+queried first to resolve MX-host A records, followed by "native"
+lookups if no answer is found in DNS. </dd>
+
+<dt><b>dnssec</b></dt>
+
+<dd>Enable <a href="https://tools.ietf.org/html/rfc4033">DNSSEC</a>
+lookups. The "dnssec" setting differs from the "enabled" setting
+above in the following ways: <ul> <li>Any MX lookups will set
+RES_USE_DNSSEC and RES_USE_EDNS0 to request DNSSEC-validated
+responses. If the MX response is DNSSEC-validated the corresponding
+hostnames are considered validated. <li> The address lookups of
+validated hostnames are also validated, (provided of course
+"<a href="postconf.5.html#smtp_host_lookup">smtp_host_lookup</a>" includes "dns", see below). <li>Temporary
+failures in DNSSEC-enabled hostname-to-address resolution block any
+"native" lookups. Additional "native" lookups only happen when
+DNSSEC lookups hard-fail (NODATA or NXDOMAIN). </ul> </dd>
+
+</dl>
+
+<p> The Postfix SMTP client considers non-MX "[nexthop]" and
+"[nexthop]:port" destinations equivalent to statically-validated
+MX records of the form "nexthop. IN MX 0 nexthop." Therefore,
+with "dnssec" support turned on, validated hostname-to-address
+lookups apply to the nexthop domain of any "[nexthop]" or
+"[nexthop]:port" destination. This is also true for LMTP "inet:host"
+and "inet:host:port" destinations, as LMTP hostnames are never
+subject to MX lookups. </p>
+
+<p>The "dnssec" setting is recommended only if you plan to use the
+<a href="TLS_README.html#client_tls_dane">dane</a> or <a
+href="TLS_README.html#client_tls_dane">dane-only</a> TLS security
+level, otherwise enabling DNSSEC support in Postfix offers no
+additional security. Postfix DNSSEC support relies on an upstream
+recursive nameserver that validates DNSSEC signatures. Such a DNS
+server will always filter out forged DNS responses, even when Postfix
+itself is not configured to use DNSSEC. </p>
+
+<p> When using Postfix DANE support the "<a href="postconf.5.html#smtp_host_lookup">smtp_host_lookup</a>" parameter
+should include "dns", as <a
+href="https://tools.ietf.org/html/rfc7672">DANE</a> is not applicable
+to hosts resolved via "native" lookups. </p>
+
+<p> As mentioned above, Postfix is not a validating <a
+href="https://tools.ietf.org/html/rfc4035#section-4.9">stub
+resolver</a>; it relies on the system's configured DNSSEC-validating
+<a href="https://tools.ietf.org/html/rfc4035#section-3.2">recursive
+nameserver</a> to perform all DNSSEC validation. Since this
+nameserver's DNSSEC-validated responses will be fully trusted, it
+is strongly recommended that the MTA host have a local DNSSEC-validating
+recursive caching nameserver listening on a loopback address, and
+be configured to use only this nameserver for all lookups. Otherwise,
+Postfix may remain subject to man-in-the-middle attacks that forge
+responses from the recursive nameserver</p>
+
+<p>DNSSEC support requires a version of Postfix compiled against a
+reasonably-modern DNS resolver(3) library that implements the
+RES_USE_DNSSEC and RES_USE_EDNS0 resolver options. </p>
+
+<p> This feature is available in Postfix 2.11 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_enforce_tls">smtp_enforce_tls</a>
+(default: no)</b></DT><DD>
+
+<p> Enforcement mode: require that remote SMTP servers use TLS
+encryption, and never send mail in the clear. This also requires
+that the remote SMTP server hostname matches the information in
+the remote server certificate, and that the remote SMTP server
+certificate was issued by a CA that is trusted by the Postfix SMTP
+client. If the certificate doesn't verify or the hostname doesn't
+match, delivery is deferred and mail stays in the queue. </p>
+
+<p> The server hostname is matched against all names provided as
+dNSNames in the SubjectAlternativeName. If no dNSNames are specified,
+the CommonName is checked. The behavior may be changed with the
+<a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a> option. </p>
+
+<p> This option is useful only if you are definitely sure that you
+will only connect to servers that support <a href="http://tools.ietf.org/html/rfc2487">RFC 2487</a> _and_ that
+provide valid server certificates. Typical use is for clients that
+send all their email to a dedicated mailhub. </p>
+
+<p> This feature is available in Postfix 2.2 and later. With
+Postfix 2.3 and later use <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> instead. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_fallback_relay">smtp_fallback_relay</a>
+(default: $<a href="postconf.5.html#fallback_relay">fallback_relay</a>)</b></DT><DD>
+
+<p>
+Optional list of relay hosts for SMTP destinations that can't be
+found or that are unreachable. With Postfix 2.2 and earlier this
+parameter is called <a href="postconf.5.html#fallback_relay">fallback_relay</a>. </p>
+
+<p>
+By default, mail is returned to the sender when a destination is
+not found, and delivery is deferred when a destination is unreachable.
+</p>
+
+<p> With bulk email deliveries, it can be beneficial to run the
+fallback relay MTA on the same host, so that it can reuse the sender
+IP address. This speeds up deliveries that are delayed by IP-based
+reputation systems (greylist, etc.). </p>
+
+<p> The fallback relays must be SMTP destinations. Specify a domain,
+host, host:port, [host]:port, [address] or [address]:port; the form
+[host] turns off MX lookups. If you specify multiple SMTP
+destinations, Postfix will try them in the specified order. </p>
+
+<p> To prevent mailer loops between MX hosts and fall-back hosts,
+Postfix version 2.2 and later will not use the fallback relays for
+destinations that it is MX host for (assuming DNS lookup is turned on).
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_generic_maps">smtp_generic_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional lookup tables that perform address rewriting in the
+Postfix SMTP client, typically to transform a locally valid address into
+a globally valid address when sending mail across the Internet.
+This is needed when the local machine does not have its own Internet
+domain name, but uses something like <i>localdomain.local</i>
+instead. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p> The table format and lookups are documented in <a href="generic.5.html">generic(5)</a>;
+examples are shown in the <a href="ADDRESS_REWRITING_README.html">ADDRESS_REWRITING_README</a> and
+<a href="STANDARD_CONFIGURATION_README.html">STANDARD_CONFIGURATION_README</a> documents. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_header_checks">smtp_header_checks</a>
+(default: empty)</b></DT><DD>
+
+<p> Restricted <a href="header_checks.5.html">header_checks(5)</a> tables for the Postfix SMTP client.
+These tables are searched while mail is being delivered. Actions
+that change the delivery time or destination are not available.
+</p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_helo_name">smtp_helo_name</a>
+(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</b></DT><DD>
+
+<p>
+The hostname to send in the SMTP HELO or EHLO command.
+</p>
+
+<p>
+The default value is the machine hostname. Specify a hostname or
+[ip.add.re.ss].
+</p>
+
+<p>
+This information can be specified in the <a href="postconf.5.html">main.cf</a> file for all SMTP
+clients, or it can be specified in the <a href="master.5.html">master.cf</a> file for a specific
+client, for example:
+</p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="master.5.html">master.cf</a>:
+ mysmtp ... smtp -o <a href="postconf.5.html#smtp_helo_name">smtp_helo_name</a>=foo.bar.com
+</pre>
+</blockquote>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_helo_timeout">smtp_helo_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The Postfix SMTP client time limit for sending the HELO or EHLO command,
+and for receiving the initial remote SMTP server response.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_host_lookup">smtp_host_lookup</a>
+(default: dns)</b></DT><DD>
+
+<p>
+What mechanisms the Postfix SMTP client uses to look up a host's
+IP address. This parameter is ignored when DNS lookups are disabled
+(see: <a href="postconf.5.html#disable_dns_lookups">disable_dns_lookups</a> and <a href="postconf.5.html#smtp_dns_support_level">smtp_dns_support_level</a>). The "dns"
+mechanism is always tried before "native" if both are listed.
+</p>
+
+<p>
+Specify one of the following:
+</p>
+
+<dl>
+
+<dt><b>dns</b></dt>
+
+<dd>Hosts can be found in the DNS (preferred). </dd>
+
+<dt><b>native</b></dt>
+
+<dd>Use the native naming service only (nsswitch.conf, or equivalent
+mechanism). </dd>
+
+<dt><b>dns, native</b></dt>
+
+<dd>Use the native service for hosts not found in the DNS. </dd>
+
+</dl>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_line_length_limit">smtp_line_length_limit</a>
+(default: 998)</b></DT><DD>
+
+<p>
+The maximal length of message header and body lines that Postfix
+will send via SMTP. This limit does not include the &lt;CR&gt;&lt;LF&gt;
+at the end of each line. Longer lines are broken by inserting
+"&lt;CR&gt;&lt;LF&gt;&lt;SPACE&gt;", to minimize the damage to MIME
+formatted mail.
+</p>
+
+<p>
+The Postfix limit of 998 characters not including &lt;CR&gt;&lt;LF&gt;
+is consistent with the SMTP limit of 1000 characters including
+&lt;CR&gt;&lt;LF&gt;. The Postfix limit was 990 with Postfix 2.8
+and earlier.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_mail_timeout">smtp_mail_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The Postfix SMTP client time limit for sending the MAIL FROM command,
+and for receiving the remote SMTP server response.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_mime_header_checks">smtp_mime_header_checks</a>
+(default: empty)</b></DT><DD>
+
+<p> Restricted mime_<a href="header_checks.5.html">header_checks(5)</a> tables for the Postfix SMTP
+client. These tables are searched while mail is being delivered.
+Actions that change the delivery time or destination are not
+available. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_mx_address_limit">smtp_mx_address_limit</a>
+(default: 5)</b></DT><DD>
+
+<p>
+The maximal number of MX (mail exchanger) IP addresses that can
+result from Postfix SMTP client mail exchanger lookups, or zero (no
+limit). Prior to
+Postfix version 2.3, this limit was disabled by default.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_mx_session_limit">smtp_mx_session_limit</a>
+(default: 2)</b></DT><DD>
+
+<p> The maximal number of SMTP sessions per delivery request before
+the Postfix SMTP client
+gives up or delivers to a fall-back <a href="postconf.5.html#relayhost">relay host</a>, or zero (no
+limit). This restriction ignores sessions that fail to complete the
+SMTP initial handshake (Postfix version 2.2 and earlier) or that fail to
+complete the EHLO and TLS handshake (Postfix version 2.3 and later). </p>
+
+<p> This feature is available in Postfix 2.1 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_nested_header_checks">smtp_nested_header_checks</a>
+(default: empty)</b></DT><DD>
+
+<p> Restricted nested_<a href="header_checks.5.html">header_checks(5)</a> tables for the Postfix SMTP
+client. These tables are searched while mail is being delivered.
+Actions that change the delivery time or destination are not
+available. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_never_send_ehlo">smtp_never_send_ehlo</a>
+(default: no)</b></DT><DD>
+
+<p> Never send EHLO at the start of an SMTP session. See also the
+<a href="postconf.5.html#smtp_always_send_ehlo">smtp_always_send_ehlo</a> parameter. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_per_record_deadline">smtp_per_record_deadline</a>
+(default: no)</b></DT><DD>
+
+<p> Change the behavior of the smtp_*_timeout time limits, from a
+time limit per read or write system call, to a time limit to send
+or receive a complete record (an SMTP command line, SMTP response
+line, SMTP message content line, or TLS protocol message). This
+limits the impact from hostile peers that trickle data one byte at
+a time. </p>
+
+<p> Note: when per-record deadlines are enabled, a short timeout
+may cause problems with TLS over very slow network connections.
+The reasons are that a TLS protocol message can be up to 16 kbytes
+long (with TLSv1), and that an entire TLS protocol message must be
+sent or received within the per-record deadline. </p>
+
+<p> This feature is available in Postfix 2.9 and later. With older
+Postfix releases, the behavior is as if this parameter is set to
+"no". </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_pix_workaround_delay_time">smtp_pix_workaround_delay_time</a>
+(default: 10s)</b></DT><DD>
+
+<p>
+How long the Postfix SMTP client pauses before sending
+".&lt;CR&gt;&lt;LF&gt;" in order to work around the PIX firewall
+"&lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;" bug.
+</p>
+
+<p>
+Choosing a too short time makes this workaround ineffective when
+sending large messages over slow network connections.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_pix_workaround_maps">smtp_pix_workaround_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Lookup tables, indexed by the remote SMTP server address, with
+per-destination workarounds for CISCO PIX firewall bugs. The table
+is not indexed by hostname for consistency with
+<a href="postconf.5.html#smtp_discard_ehlo_keyword_address_maps">smtp_discard_ehlo_keyword_address_maps</a>. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p> This feature is available in Postfix 2.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_pix_workaround_threshold_time">smtp_pix_workaround_threshold_time</a>
+(default: 500s)</b></DT><DD>
+
+<p> How long a message must be queued before the Postfix SMTP client
+turns on the PIX firewall "&lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;"
+bug workaround for delivery through firewalls with "smtp fixup"
+mode turned on. </p>
+
+<p>
+By default, the workaround is turned off for mail that is queued
+for less than 500 seconds. In other words, the workaround is normally
+turned off for the first delivery attempt.
+</p>
+
+<p>
+Specify 0 to enable the PIX firewall
+"&lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;" bug workaround upon the
+first delivery attempt.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_pix_workarounds">smtp_pix_workarounds</a>
+(default: disable_esmtp, delay_dotcrlf)</b></DT><DD>
+
+<p> A list that specifies zero or more workarounds for CISCO PIX
+firewall bugs. These workarounds are implemented by the Postfix
+SMTP client. Workaround names are separated by comma or space, and
+are case insensitive. This parameter setting can be overruled with
+per-destination <a href="postconf.5.html#smtp_pix_workaround_maps">smtp_pix_workaround_maps</a> settings. </p>
+
+<dl>
+
+<dt><b>delay_dotcrlf</b><dd> Insert a delay before sending
+".&lt;CR&gt;&lt;LF&gt;" after the end of the message content. The
+delay is subject to the <a href="postconf.5.html#smtp_pix_workaround_delay_time">smtp_pix_workaround_delay_time</a> and
+<a href="postconf.5.html#smtp_pix_workaround_threshold_time">smtp_pix_workaround_threshold_time</a> parameter settings. </dd>
+
+<dt><b>disable_esmtp</b><dd> Disable all extended SMTP commands:
+send HELO instead of EHLO. </dd>
+
+</dl>
+
+<p> This feature is available in Postfix 2.4 and later. The default
+settings are backwards compatible with earlier Postfix versions.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_quit_timeout">smtp_quit_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The Postfix SMTP client time limit for sending the QUIT command,
+and for receiving the remote SMTP server response.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_quote_rfc821_envelope">smtp_quote_rfc821_envelope</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Quote addresses in Postfix SMTP client MAIL FROM and RCPT TO commands
+as required
+by <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>. This includes putting quotes around an address localpart
+that ends in ".".
+</p>
+
+<p>
+The default is to comply with <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>. If you have to send mail to
+a broken SMTP server, configure a special SMTP client in <a href="master.5.html">master.cf</a>:
+</p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="master.5.html">master.cf</a>:
+ broken-smtp . . . smtp -o <a href="postconf.5.html#smtp_quote_rfc821_envelope">smtp_quote_rfc821_envelope</a>=no
+</pre>
+</blockquote>
+
+<p>
+and route mail for the destination in question to the "broken-smtp"
+message delivery with a <a href="transport.5.html">transport(5)</a> table.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_randomize_addresses">smtp_randomize_addresses</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Randomize the order of equal-preference MX host addresses. This
+is a performance feature of the Postfix SMTP client.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_rcpt_timeout">smtp_rcpt_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The Postfix SMTP client time limit for sending the SMTP RCPT TO
+command, and for receiving the remote SMTP server response.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_reply_filter">smtp_reply_filter</a>
+(default: empty)</b></DT><DD>
+
+<p> A mechanism to transform replies from remote SMTP servers one
+line at a time. This is a last-resort tool to work around server
+replies that break interoperability with the Postfix SMTP client.
+Other uses involve fault injection to test Postfix's handling of
+invalid responses. </p>
+
+<p> Notes: </p>
+
+<ul>
+
+<li> <p> In the case of a multi-line reply, the Postfix SMTP client
+uses the final reply line's numerical SMTP reply code and enhanced
+status code. </p>
+
+<li> <p> The numerical SMTP reply code (XYZ) takes precedence over
+the enhanced status code (X.Y.Z). When the enhanced status code
+initial digit differs from the SMTP reply code initial digit, or
+when no enhanced status code is present, the Postfix SMTP client
+uses a generic enhanced status code (X.0.0) instead. </p>
+
+</ul>
+
+<p> Specify the name of a "<a href="DATABASE_README.html">type:table</a>" lookup table. The search
+string is a single SMTP reply line as received from the remote SMTP
+server, except that the trailing &lt;CR&gt;&lt;LF&gt; are removed.
+When the lookup succeeds, the result replaces the single SMTP reply
+line. </p>
+
+<p> Examples: </p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtp_reply_filter">smtp_reply_filter</a> = <a href="pcre_table.5.html">pcre</a>:/etc/postfix/reply_filter
+</pre>
+
+<pre>
+/etc/postfix/reply_filter:
+ # Transform garbage into "250-filler..." so that it looks like
+ # one line from a multi-line reply. It does not matter what we
+ # substitute here as long it has the right syntax. The Postfix
+ # SMTP client will use the final line's numerical SMTP reply
+ # code and enhanced status code.
+ !/^([2-5][0-9][0-9]($|[- ]))/ 250-filler for garbage
+</pre>
+
+<p> This feature is available in Postfix 2.7. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_rset_timeout">smtp_rset_timeout</a>
+(default: 20s)</b></DT><DD>
+
+<p> The Postfix SMTP client time limit for sending the RSET command,
+and for receiving the remote SMTP server response. The SMTP client
+sends RSET in
+order to finish a recipient address probe, or to verify that a
+cached session is still usable. </p>
+
+<p> This feature is available in Postfix 2.1 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a>
+(default: empty)</b></DT><DD>
+
+<p> An optional table to prevent repeated SASL authentication
+failures with the same remote SMTP server hostname, username and
+password. Each table (key, value) pair contains a server name, a
+username and password, and the full server response. This information
+is stored when a remote SMTP server rejects an authentication attempt
+with a 535 reply code. As long as the <a href="postconf.5.html#smtp_sasl_password_maps">smtp_sasl_password_maps</a>
+information does no change, and as long as the <a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a>
+information does not expire (see <a href="postconf.5.html#smtp_sasl_auth_cache_time">smtp_sasl_auth_cache_time</a>) the
+Postfix SMTP client avoids SASL authentication attempts with the
+same server, username and password, and instead bounces or defers
+mail as controlled with the <a href="postconf.5.html#smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a> configuration
+parameter. </p>
+
+<p> Use a per-destination delivery concurrency of 1 (for example,
+"<a href="postconf.5.html#smtp_destination_concurrency_limit">smtp_destination_concurrency_limit</a> = 1",
+"<a href="postconf.5.html#relay_destination_concurrency_limit">relay_destination_concurrency_limit</a> = 1", etc.), otherwise multiple
+delivery agents may experience a login failure at the same time.
+</p>
+
+<p> The table must be accessed via the proxywrite service, i.e. the
+map name must start with "<a href="proxymap.8.html">proxy</a>:". The table should be stored under
+the directory specified with the <a href="postconf.5.html#data_directory">data_directory</a> parameter. </p>
+
+<p> This feature uses cryptographic hashing to protect plain-text
+passwords, and requires that Postfix is compiled with TLS support.
+</p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a> = <a href="proxymap.8.html">proxy</a>:<a href="DATABASE_README.html#types">btree</a>:/var/lib/postfix/sasl_auth_cache
+</pre>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_sasl_auth_cache_time">smtp_sasl_auth_cache_time</a>
+(default: 90d)</b></DT><DD>
+
+<p> The maximal age of an <a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a> entry before it
+is removed. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_sasl_auth_enable">smtp_sasl_auth_enable</a>
+(default: no)</b></DT><DD>
+
+<p>
+Enable SASL authentication in the Postfix SMTP client. By default,
+the Postfix SMTP client uses no authentication.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtp_sasl_auth_enable">smtp_sasl_auth_enable</a> = yes
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a>
+(default: yes)</b></DT><DD>
+
+<p> When a remote SMTP server rejects a SASL authentication request
+with a 535 reply code, defer mail delivery instead of returning
+mail as undeliverable. The latter behavior was hard-coded prior to
+Postfix version 2.5. </p>
+
+<p> Note: the setting "yes" overrides the global <a href="postconf.5.html#soft_bounce">soft_bounce</a>
+parameter, but the setting "no" does not. </p>
+
+<p> Example: </p>
+
+<pre>
+# Default as of Postfix 2.5
+<a href="postconf.5.html#smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a> = yes
+# The old hard-coded default
+<a href="postconf.5.html#smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a> = no
+</pre>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a>
+(default: empty)</b></DT><DD>
+
+<p>
+If non-empty, a Postfix SMTP client filter for the remote SMTP
+server's list of offered SASL mechanisms. Different client and
+server implementations may support different mechanism lists; by
+default, the Postfix SMTP client will use the intersection of the
+two. <a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a> specifies an optional third mechanism
+list to intersect with. </p>
+
+<p> Specify mechanism names, "/file/name" patterns or "<a href="DATABASE_README.html">type:table</a>"
+lookup tables. The right-hand side result from "<a href="DATABASE_README.html">type:table</a>" lookups
+is ignored. Specify "!pattern" to exclude a mechanism name from the
+list. The form "!/file/name" is supported only in Postfix version
+2.4 and later. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a> = plain, login
+<a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a> = /etc/postfix/smtp_mechs
+<a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a> = !gssapi, !login, <a href="DATABASE_README.html#types">static</a>:rest
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtp_sasl_password_maps">smtp_sasl_password_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional Postfix SMTP client lookup tables with one username:password
+entry per sender, remote hostname or next-hop domain. Per-sender
+lookup is done only when sender-dependent authentication is enabled.
+If no username:password entry is found, then the Postfix SMTP client
+will not attempt to authenticate to the remote host.
+</p>
+
+<p>
+The Postfix SMTP client opens the lookup table before going to
+chroot jail, so you can leave the password file in /etc/postfix.
+</p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_sasl_path">smtp_sasl_path</a>
+(default: empty)</b></DT><DD>
+
+<p> Implementation-specific information that the Postfix SMTP client
+passes through to
+the SASL plug-in implementation that is selected with
+<b><a href="postconf.5.html#smtp_sasl_type">smtp_sasl_type</a></b>. Typically this specifies the name of a
+configuration file or rendezvous point. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_sasl_security_options">smtp_sasl_security_options</a>
+(default: noplaintext, noanonymous)</b></DT><DD>
+
+<p> Postfix SMTP client SASL security options; as of Postfix 2.3
+the list of available
+features depends on the SASL client implementation that is selected
+with <b><a href="postconf.5.html#smtp_sasl_type">smtp_sasl_type</a></b>. </p>
+
+<p> The following security features are defined for the <b>cyrus</b>
+client SASL implementation: </p>
+
+<p>
+Specify zero or more of the following:
+</p>
+
+<dl>
+
+<dt><b>noplaintext</b></dt>
+
+<dd>Disallow methods that use plaintext passwords. </dd>
+
+<dt><b>noactive</b></dt>
+
+<dd>Disallow methods subject to active (non-dictionary) attack.
+</dd>
+
+<dt><b>nodictionary</b></dt>
+
+<dd>Disallow methods subject to passive (dictionary) attack. </dd>
+
+<dt><b>noanonymous</b></dt>
+
+<dd>Disallow methods that allow anonymous authentication. </dd>
+
+<dt><b>mutual_auth</b></dt>
+
+<dd>Only allow methods that provide mutual authentication (not
+available with SASL version 1). </dd>
+
+</dl>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtp_sasl_security_options">smtp_sasl_security_options</a> = noplaintext
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtp_sasl_tls_security_options">smtp_sasl_tls_security_options</a>
+(default: $<a href="postconf.5.html#smtp_sasl_security_options">smtp_sasl_security_options</a>)</b></DT><DD>
+
+<p> The SASL authentication security options that the Postfix SMTP
+client uses for TLS encrypted SMTP sessions. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_sasl_tls_verified_security_options">smtp_sasl_tls_verified_security_options</a>
+(default: $<a href="postconf.5.html#smtp_sasl_tls_security_options">smtp_sasl_tls_security_options</a>)</b></DT><DD>
+
+<p> The SASL authentication security options that the Postfix SMTP
+client uses for TLS encrypted SMTP sessions with a verified server
+certificate. </p>
+
+<p> When mail is sent to the public MX host for the recipient's
+domain, server certificates are by default optional, and delivery
+proceeds even if certificate verification fails. For delivery via
+a submission service that requires SASL authentication, it may be
+appropriate to send plaintext passwords only when the connection
+to the server is strongly encrypted <b>and</b> the server identity
+is verified. </p>
+
+<p> The <a href="postconf.5.html#smtp_sasl_tls_verified_security_options">smtp_sasl_tls_verified_security_options</a> parameter makes it
+possible to only enable plaintext mechanisms when a secure connection
+to the server is available. Submission servers subject to this
+policy must either have verifiable certificates or offer suitable
+non-plaintext SASL mechanisms. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_sasl_type">smtp_sasl_type</a>
+(default: cyrus)</b></DT><DD>
+
+<p> The SASL plug-in type that the Postfix SMTP client should use
+for authentication. The available types are listed with the
+"<b>postconf -A</b>" command. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_send_dummy_mail_auth">smtp_send_dummy_mail_auth</a>
+(default: no)</b></DT><DD>
+
+<p> Whether or not to append the "AUTH=&lt;&gt;" option to the MAIL
+FROM command in SASL-authenticated SMTP sessions. The default is
+not to send this, to avoid problems with broken remote SMTP servers.
+Before Postfix 2.9 the behavior is as if "<a href="postconf.5.html#smtp_send_dummy_mail_auth">smtp_send_dummy_mail_auth</a>
+= yes".
+
+<p> This feature is available in Postfix 2.9 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_send_xforward_command">smtp_send_xforward_command</a>
+(default: no)</b></DT><DD>
+
+<p>
+Send the non-standard XFORWARD command when the Postfix SMTP server
+EHLO response announces XFORWARD support.
+</p>
+
+<p>
+This allows a Postfix SMTP delivery agent, used for injecting mail
+into
+a content filter, to forward the name, address, protocol and HELO
+name of the original client to the content filter and downstream
+queuing SMTP server. This can produce more useful logging than
+localhost[127.0.0.1] etc.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_sender_dependent_authentication">smtp_sender_dependent_authentication</a>
+(default: no)</b></DT><DD>
+
+<p>
+Enable sender-dependent authentication in the Postfix SMTP client; this is
+available only with SASL authentication, and disables SMTP connection
+caching to ensure that mail from different senders will use the
+appropriate credentials. </p>
+
+<p>
+This feature is available in Postfix 2.3 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_skip_4xx_greeting">smtp_skip_4xx_greeting</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Skip SMTP servers that greet with a 4XX status code (go away, try
+again later).
+</p>
+
+<p>
+By default, the Postfix SMTP client moves on the next mail exchanger.
+Specify
+"<a href="postconf.5.html#smtp_skip_4xx_greeting">smtp_skip_4xx_greeting</a> = no" if Postfix should defer delivery
+immediately.
+</p>
+
+<p> This feature is available in Postfix 2.0 and earlier.
+Later Postfix versions always skip remote SMTP servers that greet
+with a
+4XX status code. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_skip_5xx_greeting">smtp_skip_5xx_greeting</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Skip remote SMTP servers that greet with a 5XX status code.
+</p>
+
+<p> By default, the Postfix SMTP client moves on the next mail
+exchanger. Specify "<a href="postconf.5.html#smtp_skip_5xx_greeting">smtp_skip_5xx_greeting</a> = no" if Postfix should
+bounce the mail immediately. Caution: the latter behavior appears
+to contradict <a href="http://tools.ietf.org/html/rfc2821">RFC 2821</a>. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_skip_quit_response">smtp_skip_quit_response</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Do not wait for the response to the SMTP QUIT command.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_starttls_timeout">smtp_starttls_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p> Time limit for Postfix SMTP client write and read operations
+during TLS startup and shutdown handshake procedures. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tcp_port">smtp_tcp_port</a>
+(default: smtp)</b></DT><DD>
+
+<p>
+The default TCP port that the Postfix SMTP client connects to.
+Specify a symbolic name (see services(5)) or a numeric port.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_CAfile">smtp_tls_CAfile</a>
+(default: empty)</b></DT><DD>
+
+<p> A file containing CA certificates of root CAs trusted to sign
+either remote SMTP server certificates or intermediate CA certificates.
+These are loaded into memory before the <a href="smtp.8.html">smtp(8)</a> client enters the
+chroot jail. If the number of trusted roots is large, consider using
+<a href="postconf.5.html#smtp_tls_CApath">smtp_tls_CApath</a> instead, but note that the latter directory must be
+present in the chroot jail if the <a href="smtp.8.html">smtp(8)</a> client is chrooted. This
+file may also be used to augment the client certificate trust chain,
+but it is best to include all the required certificates directly in
+$<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> (or, Postfix &ge; 3.4 $<a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a>). </p>
+
+<p> Specify "<a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a> = /path/to/system_CA_file" to use
+ONLY the system-supplied default Certification Authority certificates.
+</p>
+
+<p> Specify "<a href="postconf.5.html#tls_append_default_CA">tls_append_default_CA</a> = no" to prevent Postfix from
+appending the system-supplied default CAs and trusting third-party
+certificates. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a> = /etc/postfix/CAcert.pem
+</pre>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_CApath">smtp_tls_CApath</a>
+(default: empty)</b></DT><DD>
+
+<p> Directory with PEM format Certification Authority certificates
+that the Postfix SMTP client uses to verify a remote SMTP server
+certificate. Don't forget to create the necessary "hash" links
+with, for example, "$OPENSSL_HOME/bin/c_rehash /etc/postfix/certs".
+</p>
+
+<p> To use this option in chroot mode, this directory (or a copy)
+must be inside the chroot jail. </p>
+
+<p> Specify "<a href="postconf.5.html#smtp_tls_CApath">smtp_tls_CApath</a> = /path/to/system_CA_directory" to
+use ONLY the system-supplied default Certification Authority certificates.
+</p>
+
+<p> Specify "<a href="postconf.5.html#tls_append_default_CA">tls_append_default_CA</a> = no" to prevent Postfix from
+appending the system-supplied default CAs and trusting third-party
+certificates. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtp_tls_CApath">smtp_tls_CApath</a> = /etc/postfix/certs
+</pre>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_block_early_mail_reply">smtp_tls_block_early_mail_reply</a>
+(default: no)</b></DT><DD>
+
+<p> Try to detect a mail hijacking attack based on a TLS protocol
+vulnerability (CVE-2009-3555), where an attacker prepends malicious
+HELO, MAIL, RCPT, DATA commands to a Postfix SMTP client TLS session.
+The attack would succeed with non-Postfix SMTP servers that reply
+to the malicious HELO, MAIL, RCPT, DATA commands after negotiating
+the Postfix SMTP client TLS session. </p>
+
+<p> This feature is available in Postfix 2.7. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_cert_file">smtp_tls_cert_file</a>
+(default: empty)</b></DT><DD>
+
+<p> File with the Postfix SMTP client RSA certificate in PEM format.
+This file may also contain the Postfix SMTP client private RSA key, and
+these may be the same as the Postfix SMTP server RSA certificate and key
+file. With Postfix &ge; 3.4 the preferred way to configure client keys
+and certificates is via the "<a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a>" parameter. </p>
+
+<p> Do not configure client certificates unless you <b>must</b> present
+client TLS certificates to one or more servers. Client certificates are
+not usually needed, and can cause problems in configurations that work
+well without them. The recommended setting is to let the defaults stand: </p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> =
+<a href="postconf.5.html#smtp_tls_key_file">smtp_tls_key_file</a> =
+<a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a> =
+<a href="postconf.5.html#smtp_tls_eckey_file">smtp_tls_eckey_file</a> =
+# Obsolete DSA parameters
+<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a> =
+<a href="postconf.5.html#smtp_tls_dkey_file">smtp_tls_dkey_file</a> =
+# Postfix &ge; 3.4 interface
+<a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a> =
+</pre>
+</blockquote>
+
+<p> The best way to use the default settings is to comment out the above
+parameters in <a href="postconf.5.html">main.cf</a> if present. </p>
+
+<p> To enable remote SMTP servers to verify the Postfix SMTP client
+certificate, the issuing CA certificates must be made available to the
+server. You should include the required certificates in the client
+certificate file, the client certificate first, then the issuing
+CA(s) (bottom-up order). </p>
+
+<p> Example: the certificate for "client.example.com" was issued by
+"intermediate CA" which itself has a certificate issued by "root CA".
+As the "root" super-user create the client.pem file with: </p>
+
+<blockquote>
+<pre>
+# <b>umask 077</b>
+# <b>cat client_key.pem client_cert.pem intermediate_CA.pem &gt; chain.pem </b>
+</pre>
+</blockquote>
+
+<p> If you also want to verify remote SMTP server certificates issued by
+these CAs, you can add the CA certificates to the <a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a>, in
+which case it is not necessary to have them in the <a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>,
+<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a> (obsolete) or <a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a>. </p>
+
+<p> A certificate supplied here must be usable as an SSL client certificate
+and hence pass the "openssl verify -purpose sslclient ..." test. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> = /etc/postfix/chain.pem
+</pre>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_chain_files">smtp_tls_chain_files</a>
+(default: empty)</b></DT><DD>
+
+<p> List of one or more PEM files, each holding one or more private keys
+directly followed by a corresponding certificate chain. The file names
+are separated by commas and/or whitespace. This parameter obsoletes the
+legacy algorithm-specific key and certificate file settings. When this
+parameter is non-empty, the legacy parameters are ignored, and a warning
+is logged if any are also non-empty. </p>
+
+<p> With the proliferation of multiple private key algorithms&mdash;which,
+as of OpenSSL 1.1.1, include DSA (obsolete), RSA, ECDSA, Ed25519
+and Ed448&mdash;it is increasingly impractical to use separate
+parameters to configure the key and certificate chain for each
+algorithm. Therefore, Postfix now supports storing multiple keys and
+corresponding certificate chains in a single file or in a set of files.
+
+<p> Each key must appear <b>immediately before</b> the corresponding
+certificate, optionally followed by additional issuer certificates that
+complete the certificate chain for that key. When multiple files are
+specified, they are equivalent to a single file that is concatenated
+from those files in the given order. Thus, while a key must always
+precede its certificate and issuer chain, it can be in a separate file,
+so long as that file is listed immediately before the file that holds
+the corresponding certificate chain. Once all the files are
+concatenated, the sequence of PEM objects must be: <i>key1, cert1,
+[chain1], key2, cert2, [chain2], ..., keyN, certN, [chainN].</i> </p>
+
+<p> Storing the private key in the same file as the corresponding
+certificate is more reliable. With the key and certificate in separate
+files, there is a chance that during key rollover a Postfix process
+might load a private key and certificate from separate files that don't
+match. Various operational errors may even result in a persistent
+broken configuration in which the certificate does not match the private
+key. </p>
+
+<p> The file or files must contain at most one key of each type. If,
+for example, two or more RSA keys and corresponding chains are listed,
+depending on the version of OpenSSL either only the last one will be
+used or an configuration error may be detected. Note that while
+"Ed25519" and "Ed448" are considered separate algorithms, the various
+ECDSA curves (typically one of prime256v1, secp384r1 or secp521r1) are
+considered as different parameters of a single "ECDSA" algorithm, so it
+is not presently possible to configure keys for more than one ECDSA
+curve. </p>
+
+<p>
+Example (separate files for each key and corresponding certificate chain):
+</p>
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a> =
+ ${<a href="postconf.5.html#config_directory">config_directory</a>}/ed25519.pem,
+ ${<a href="postconf.5.html#config_directory">config_directory</a>}/ed448.pem,
+ ${<a href="postconf.5.html#config_directory">config_directory</a>}/rsa.pem
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/ed25519.pem:
+ -----BEGIN PRIVATE KEY-----
+ MC4CAQAwBQYDK2VwBCIEIEJfbbO4BgBQGBg9NAbIJaDBqZb4bC4cOkjtAH+Efbz3
+ -----END PRIVATE KEY-----
+ -----BEGIN CERTIFICATE-----
+ MIIBKzCB3qADAgECAhQaw+rflRreYuUZBp0HuNn/e5rMZDAFBgMrZXAwFDESMBAG
+ ...
+ nC0egv51YPDWxEHom4QA
+ -----END CERTIFICATE-----
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/ed448.pem:
+ -----BEGIN PRIVATE KEY-----
+ MEcCAQAwBQYDK2VxBDsEOQf+m0P+G0qi+NZ0RolyeiE5zdlPQR8h8y4jByBifpIe
+ LNler7nzHQJ1SLcOiXFHXlxp/84VZuh32A==
+ -----END PRIVATE KEY-----
+ -----BEGIN CERTIFICATE-----
+ MIIBdjCB96ADAgECAhQSv4oP972KypOZPNPF4fmsiQoRHzAFBgMrZXEwFDESMBAG
+ ...
+ pQcWsx+4J29e6YWH3Cy/CdUaexKP4RPCZDrPX7bk5C2BQ+eeYOxyThMA
+ -----END CERTIFICATE-----
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/rsa.pem:
+ -----BEGIN PRIVATE KEY-----
+ MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDc4QusgkahH9rL
+ ...
+ ahQkZ3+krcaJvDSMgvu0tDc=
+ -----END PRIVATE KEY-----
+ -----BEGIN CERTIFICATE-----
+ MIIC+DCCAeCgAwIBAgIUIUkrbk1GAemPCT8i9wKsTGDH7HswDQYJKoZIhvcNAQEL
+ ...
+ Rirz15HGVNTK8wzFd+nulPzwUo6dH2IU8KazmyRi7OGvpyrMlm15TRE2oyE=
+ -----END CERTIFICATE-----
+</pre>
+</blockquote>
+
+<p>
+Example (all keys and certificates in a single file):
+</p>
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a> = ${<a href="postconf.5.html#config_directory">config_directory</a>}/chains.pem
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/chains.pem:
+ -----BEGIN PRIVATE KEY-----
+ MC4CAQAwBQYDK2VwBCIEIEJfbbO4BgBQGBg9NAbIJaDBqZb4bC4cOkjtAH+Efbz3
+ -----END PRIVATE KEY-----
+ -----BEGIN CERTIFICATE-----
+ MIIBKzCB3qADAgECAhQaw+rflRreYuUZBp0HuNn/e5rMZDAFBgMrZXAwFDESMBAG
+ ...
+ nC0egv51YPDWxEHom4QA
+ -----END CERTIFICATE-----
+ -----BEGIN PRIVATE KEY-----
+ MEcCAQAwBQYDK2VxBDsEOQf+m0P+G0qi+NZ0RolyeiE5zdlPQR8h8y4jByBifpIe
+ LNler7nzHQJ1SLcOiXFHXlxp/84VZuh32A==
+ -----END PRIVATE KEY-----
+ -----BEGIN CERTIFICATE-----
+ MIIBdjCB96ADAgECAhQSv4oP972KypOZPNPF4fmsiQoRHzAFBgMrZXEwFDESMBAG
+ ...
+ pQcWsx+4J29e6YWH3Cy/CdUaexKP4RPCZDrPX7bk5C2BQ+eeYOxyThMA
+ -----END CERTIFICATE-----
+ -----BEGIN PRIVATE KEY-----
+ MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDc4QusgkahH9rL
+ ...
+ ahQkZ3+krcaJvDSMgvu0tDc=
+ -----END PRIVATE KEY-----
+ -----BEGIN CERTIFICATE-----
+ MIIC+DCCAeCgAwIBAgIUIUkrbk1GAemPCT8i9wKsTGDH7HswDQYJKoZIhvcNAQEL
+ ...
+ Rirz15HGVNTK8wzFd+nulPzwUo6dH2IU8KazmyRi7OGvpyrMlm15TRE2oyE=
+ -----END CERTIFICATE-----
+</pre>
+</blockquote>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_cipherlist">smtp_tls_cipherlist</a>
+(default: empty)</b></DT><DD>
+
+<p> Obsolete Postfix &lt; 2.3 control for the Postfix SMTP client TLS
+cipher list. As this feature applies to all TLS security levels, it is easy
+to create interoperability problems by choosing a non-default cipher
+list. Do not use a non-default TLS cipher list on hosts that deliver email
+to the public Internet: you will be unable to send email to servers that
+only support the ciphers you exclude. Using a restricted cipher list
+may be more appropriate for an internal MTA, where one can exert some
+control over the TLS software and settings of the peer servers. </p>
+
+<p> <b>Note:</b> do not use "" quotes around the parameter value. </p>
+
+<p> This feature is available in Postfix version 2.2. It is not used with
+Postfix 2.3 and later; use <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> instead. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_ciphers">smtp_tls_ciphers</a>
+(default: medium)</b></DT><DD>
+
+<p> The minimum TLS cipher grade that the Postfix SMTP client
+will use with opportunistic TLS encryption. Cipher types listed in
+<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> are excluded from the base definition of
+the selected cipher grade. The default value is "medium" for
+Postfix releases after the middle of 2015, "export" for older
+releases. </p>
+
+<p> When TLS is mandatory the cipher grade is chosen via the
+<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> configuration parameter, see there for syntax
+details. See <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> for information on how to configure
+ciphers on a per-destination basis. </p>
+
+<p> This feature is available in Postfix 2.6 and later. With earlier Postfix
+releases only the <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> parameter is implemented,
+and opportunistic TLS always uses "export" or better (i.e. all) ciphers. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_connection_reuse">smtp_tls_connection_reuse</a>
+(default: no)</b></DT><DD>
+
+<p> Try to make multiple deliveries per TLS-encrypted connection.
+This uses the <a href="tlsproxy.8.html">tlsproxy(8)</a> service to encrypt an SMTP connection,
+uses the <a href="scache.8.html">scache(8)</a> service to save that connection, and relies on
+hints from the <a href="qmgr.8.html">qmgr(8)</a> daemon. </p>
+
+<p> See "<a href="TLS_README.html#client_tls_reuse">Client-side
+TLS connection reuse</a>" for background details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_dane_insecure_mx_policy">smtp_tls_dane_insecure_mx_policy</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The TLS policy for MX hosts with "secure" TLSA records when the
+nexthop destination security level is <b>dane</b>, but the MX
+record was found via an "insecure" MX lookup. The choices are:
+</p>
+
+<dl>
+<dt><b>may</b></dt>
+<dd> The TLSA records will be ignored and TLS will be optional. If
+the MX host does not appear to support STARTTLS, or the STARTTLS
+handshake fails, mail may be sent in the clear. </dd>
+<dt><b>encrypt</b></dt>
+<dd> The TLSA records will signal a requirement to use TLS. While
+TLS encryption will be required, authentication will not be performed.
+</dd>
+<dt><b>dane</b> (default)</dt>
+<dd>The TLSA records will be used just as with "secure" MX records.
+TLS encryption will be required, and, if at least one of the TLSA
+records is "usable", authentication will be required. When
+authentication succeeds, it will be logged only as "Trusted", not
+"Verified", because the MX host name could have been forged. </dd>
+</dl>
+
+<p> The default setting for Postfix &ge; 3.6 is "dane" with
+"<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = dane", otherwise "may". This behavior
+was backported to Postfix versions 3.5.9, 3.4.19, 3.3.16. 3.2.21.
+With earlier
+Postfix versions the default setting was always "dane". </p>
+
+<p> Though with "insecure" MX records an active attacker can
+compromise SMTP transport security by returning forged MX records,
+such attacks are "tamper-evident" since any forged MX hostnames
+will be recorded in the mail logs. Attackers who place a high value
+staying hidden may be deterred from forging MX records. </p>
+
+<p>
+This feature is available in Postfix 3.1 and later. The <b>may</b>
+policy is backwards-compatible with earlier Postfix versions.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_dcert_file">smtp_tls_dcert_file</a>
+(default: empty)</b></DT><DD>
+
+<p> File with the Postfix SMTP client DSA certificate in PEM format.
+This file may also contain the Postfix SMTP client private DSA key.
+The DSA algorithm is obsolete and should not be used. </p>
+
+<p> See the discussion under <a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> for more details.
+</p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a> = /etc/postfix/client-dsa.pem
+</pre>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_dkey_file">smtp_tls_dkey_file</a>
+(default: $<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a>)</b></DT><DD>
+
+<p> File with the Postfix SMTP client DSA private key in PEM format.
+This file may be combined with the Postfix SMTP client DSA certificate
+file specified with $<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a>. The DSA algorithm is obsolete
+and should not be used. </p>
+
+<p> The private key must be accessible without a pass-phrase, i.e. it
+must not be encrypted. File permissions should grant read-only
+access to the system superuser account ("root"), and no access
+to anyone else. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_eccert_file">smtp_tls_eccert_file</a>
+(default: empty)</b></DT><DD>
+
+<p> File with the Postfix SMTP client ECDSA certificate in PEM format.
+This file may also contain the Postfix SMTP client ECDSA private key.
+With Postfix &ge; 3.4 the preferred way to configure client keys and
+certificates is via the "<a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a>" parameter. </p>
+
+<p> See the discussion under <a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> for more details.
+</p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a> = /etc/postfix/ecdsa-ccert.pem
+</pre>
+
+<p> This feature is available in Postfix 2.6 and later, when Postfix is
+compiled and linked with OpenSSL 1.0.0 or later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_eckey_file">smtp_tls_eckey_file</a>
+(default: $<a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a>)</b></DT><DD>
+
+<p> File with the Postfix SMTP client ECDSA private key in PEM format.
+This file may be combined with the Postfix SMTP client ECDSA certificate
+file specified with $<a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a>. With Postfix &ge; 3.4 the
+preferred way to configure client keys and certificates is via the
+"<a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a>" parameter. </p>
+
+<p> The private key must be accessible without a pass-phrase, i.e. it
+must not be encrypted. File permissions should grant read-only
+access to the system superuser account ("root"), and no access
+to anyone else. </p>
+
+<p> This feature is available in Postfix 2.6 and later, when Postfix is
+compiled and linked with OpenSSL 1.0.0 or later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_enforce_peername">smtp_tls_enforce_peername</a>
+(default: yes)</b></DT><DD>
+
+<p> With mandatory TLS encryption, require that the remote SMTP
+server hostname matches the information in the remote SMTP server
+certificate. As of <a href="http://tools.ietf.org/html/rfc2487">RFC 2487</a> the requirements for hostname checking
+for MTA clients are not specified. </p>
+
+<p> This option can be set to "no" to disable strict peer name
+checking. This setting has no effect on sessions that are controlled
+via the <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> table. </p>
+
+<p> Disabling the hostname verification can make sense in closed
+environment where special CAs are created. If not used carefully,
+this option opens the danger of a "man-in-the-middle" attack (the
+CommonName of this attacker will be logged). </p>
+
+<p> This feature is available in Postfix 2.2 and later. With
+Postfix 2.3 and later use <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> instead. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a>
+(default: empty)</b></DT><DD>
+
+<p> List of ciphers or cipher types to exclude from the Postfix
+SMTP client cipher
+list at all TLS security levels. This is not an OpenSSL cipherlist, it is
+a simple list separated by whitespace and/or commas. The elements are a
+single cipher, or one or more "+" separated cipher properties, in which
+case only ciphers matching <b>all</b> the properties are excluded. </p>
+
+<p> Examples (some of these will cause problems): </p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> = aNULL
+<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> = MD5, DES
+<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> = DES+MD5
+<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> = AES256-SHA, DES-CBC3-MD5
+<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> = kEDH+aRSA
+</pre>
+</blockquote>
+
+<p> The first setting, disables anonymous ciphers. The next setting
+disables ciphers that use the MD5 digest algorithm or the (single) DES
+encryption algorithm. The next setting disables ciphers that use MD5 and
+DES together. The next setting disables the two ciphers "AES256-SHA"
+and "DES-CBC3-MD5". The last setting disables ciphers that use "EDH"
+key exchange with RSA authentication. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a>
+(default: empty)</b></DT><DD>
+
+<p> List of acceptable remote SMTP server certificate fingerprints for
+the "fingerprint" TLS security level (<b><a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a></b> =
+fingerprint). At this security level, Certification Authorities are not
+used, and certificate expiration times are ignored. Instead, server
+certificates are verified directly via their certificate fingerprint
+or public key fingerprint (Postfix 2.9 and later). The fingerprint
+is a message digest of the server certificate (or public key). The
+digest algorithm is selected via the <b><a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a></b>
+parameter. </p>
+
+<p> When an <b><a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a></b> table entry specifies the
+"fingerprint" security level, any "match" attributes in that entry specify
+the list of valid fingerprints for the corresponding destination. Multiple
+fingerprints can be combined with a "|" delimiter in a single match
+attribute, or multiple match attributes can be employed. </p>
+
+<p> Example: Certificate fingerprint verification with internal mailhub.
+Two matching fingerprints are listed. The <a href="postconf.5.html#relayhost">relayhost</a> may be multiple
+physical hosts behind a load-balancer, each with its own private/public
+key and self-signed certificate. Alternatively, a single <a href="postconf.5.html#relayhost">relayhost</a> may
+be in the process of switching from one set of private/public keys to
+another, and both keys are trusted just prior to the transition. </p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#relayhost">relayhost</a> = [mailhub.example.com]
+<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = fingerprint
+<a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a> = md5
+<a href="postconf.5.html#smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a> =
+ 3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
+ EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35
+</pre>
+</blockquote>
+
+<p> Example: Certificate fingerprint verification with selected destinations.
+As in the example above, we show two matching fingerprints: </p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/tls_policy
+ <a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a> = md5
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/tls_policy:
+ example.com fingerprint
+ match=3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
+ match=EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35
+</pre>
+</blockquote>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a>
+(default: md5)</b></DT><DD>
+
+<p> The message digest algorithm used to construct remote SMTP server
+certificate fingerprints. At the "fingerprint" TLS security level
+(<b><a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a></b> = fingerprint), the server certificate is
+verified by directly matching its certificate fingerprint or its public
+key fingerprint (Postfix 2.9 and later). The fingerprint is the
+message digest of the server certificate (or its public key)
+using the selected
+algorithm. With a digest algorithm resistant to "second pre-image"
+attacks, it is not feasible to create a new public key and a matching
+certificate (or public/private key-pair) that has the same fingerprint. </p>
+
+<p> The default algorithm is <b>md5</b>; this is consistent with
+the backwards compatible setting of the digest used to verify client
+certificates in the SMTP server. </p>
+
+<p> The best practice algorithm is now <b>sha1</b>. Recent advances in hash
+function cryptanalysis have led to md5 being deprecated in favor of sha1.
+However, as long as there are no known "second pre-image" attacks
+against md5, its use in this context can still be considered safe.
+</p>
+
+<p> While additional digest algorithms are often available with OpenSSL's
+libcrypto, only those used by libssl in SSL cipher suites are available to
+Postfix. For now this means just md5 or sha1. </p>
+
+<p> To find the fingerprint of a specific certificate file, with a
+specific digest algorithm, run:
+</p>
+
+<blockquote>
+<pre>
+$ openssl x509 -noout -fingerprint -<i>digest</i> -in <i>certfile</i>.pem
+</pre>
+</blockquote>
+
+<p> The text to the right of "=" sign is the desired fingerprint.
+For example: </p>
+
+<blockquote>
+<pre>
+$ openssl x509 -noout -fingerprint -sha1 -in cert.pem
+SHA1 Fingerprint=D4:6A:AB:19:24:79:F8:32:BB:A6:CB:66:82:C0:8E:9B:EE:29:A8:1A
+</pre>
+</blockquote>
+
+<p> To extract the public key fingerprint from an X.509 certificate,
+you need to extract the public key from the certificate and compute
+the appropriate digest of its DER (ASN.1) encoding. With OpenSSL
+the "-pubkey" option of the "x509" command extracts the public
+key always in "PEM" format. We pipe the result to another OpenSSL
+command that converts the key to DER and then to the "dgst" command
+to compute the fingerprint. </p>
+
+<p> The actual command to transform the key to DER format depends
+on the version of OpenSSL used. With OpenSSL 1.0.0 and later, the
+"pkey" command supports all key types. With OpenSSL 0.9.8 and
+earlier, the key type is always RSA (nobody uses DSA, and EC
+keys are not fully supported by 0.9.8), so the "rsa" command is
+used. </p>
+<blockquote>
+<pre>
+# OpenSSL 1.0 with all certificates and SHA-1 fingerprints.
+$ openssl x509 -in cert.pem -noout -pubkey |
+ openssl pkey -pubin -outform DER |
+ openssl dgst -sha1 -c
+(stdin)= 64:3f:1f:f6:e5:1e:d4:2a:56:8b:fc:09:1a:61:98:b5:bc:7c:60:58
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+# OpenSSL 0.9.8 with RSA certificates and MD5 fingerprints.
+$ openssl x509 -in cert.pem -noout -pubkey |
+ openssl rsa -pubin -outform DER |
+ openssl dgst -md5 -c
+(stdin)= f4:62:60:f6:12:8f:d5:8d:28:4d:13:a7:db:b2:ff:50
+</pre>
+</blockquote>
+
+<p> The Postfix SMTP server and client log the peer (leaf) certificate
+fingerprint and public key fingerprint when the TLS loglevel is 2 or
+higher. </p>
+
+<p> <b>Note:</b> Postfix 2.9.0&ndash;2.9.5 computed the public key
+fingerprint incorrectly. To use public-key fingerprints, upgrade
+to Postfix 2.9.6 or later. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_force_insecure_host_tlsa_lookup">smtp_tls_force_insecure_host_tlsa_lookup</a>
+(default: no)</b></DT><DD>
+
+<p> Lookup the associated DANE TLSA RRset even when a hostname is
+not an alias and its address records lie in an unsigned zone. This
+is unlikely to ever yield DNSSEC validated results, since child
+zones of unsigned zones are also unsigned in the absence of DLV or
+locally configured non-root trust-anchors. We anticipate that such
+mechanisms will not be used for just the "_tcp" subdomain of a host.
+Suppressing the TLSA RRset lookup reduces latency and avoids potential
+interoperability problems with nameservers for unsigned zones that
+are not prepared to handle the new TLSA RRset. </p>
+
+<p> This feature is available in Postfix 2.11. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_key_file">smtp_tls_key_file</a>
+(default: $<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>)</b></DT><DD>
+
+<p> File with the Postfix SMTP client RSA private key in PEM format.
+This file may be combined with the Postfix SMTP client RSA certificate
+file specified with $<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>. With Postfix &ge; 3.4 the
+preferred way to configure client keys and certificates is via the
+"<a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a>" parameter. </p>
+
+<p> The private key must be accessible without a pass-phrase, i.e. it
+must not be encrypted. File permissions should grant read-only
+access to the system superuser account ("root"), and no access
+to anyone else. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtp_tls_key_file">smtp_tls_key_file</a> = $<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>
+</pre>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_loglevel">smtp_tls_loglevel</a>
+(default: 0)</b></DT><DD>
+
+<p> Enable additional Postfix SMTP client logging of TLS activity.
+Each logging level also includes the information that is logged at
+a lower logging level. </p>
+
+<dl compact>
+
+<dt> </dt> <dd> 0 Disable logging of TLS activity. </dd>
+
+<dt> </dt> <dd> 1 Log only a summary message on TLS handshake completion
+&mdash; no logging of remote SMTP server certificate trust-chain
+verification errors if server certificate verification is not required.
+With Postfix 2.8 and earlier, log the summary message and unconditionally
+log trust-chain verification errors. </dd>
+
+<dt> </dt> <dd> 2 Also log levels during TLS negotiation. </dd>
+
+<dt> </dt> <dd> 3 Also log hexadecimal and ASCII dump of TLS negotiation
+process. </dd>
+
+<dt> </dt> <dd> 4 Also log hexadecimal and ASCII dump of complete
+transmission after STARTTLS. </dd>
+
+</dl>
+
+<p> Do not use "<a href="postconf.5.html#smtp_tls_loglevel">smtp_tls_loglevel</a> = 2" or higher except in case of
+problems. Use of loglevel 4 is strongly discouraged. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a>
+(default: medium)</b></DT><DD>
+
+<p> The minimum TLS cipher grade that the Postfix SMTP client will
+use with
+mandatory TLS encryption. The default value "medium" is suitable
+for most destinations with which you may want to enforce TLS, and
+is beyond the reach of today's cryptanalytic methods. See
+<a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> for information on how to configure ciphers
+on a per-destination basis. </p>
+
+<p> The following cipher grades are supported: </p>
+
+<dl>
+<dt><b>export</b></dt>
+<dd> Enable "EXPORT" grade or better OpenSSL ciphers. The underlying
+cipherlist is specified via the <a href="postconf.5.html#tls_export_cipherlist">tls_export_cipherlist</a> configuration
+parameter, which you are strongly encouraged to not change. This
+choice is insecure and SHOULD NOT be used. </dd>
+
+<dt><b>low</b></dt>
+<dd> Enable "LOW" grade or better OpenSSL ciphers. The underlying
+cipherlist is specified via the <a href="postconf.5.html#tls_low_cipherlist">tls_low_cipherlist</a> configuration
+parameter, which you are strongly encouraged to not change. This
+choice is insecure and SHOULD NOT be used. </dd>
+
+<dt><b>medium</b></dt>
+<dd> Enable "MEDIUM" grade or better OpenSSL ciphers.
+The underlying cipherlist is specified via the <a href="postconf.5.html#tls_medium_cipherlist">tls_medium_cipherlist</a>
+configuration parameter, which you are strongly encouraged to not change.
+</dd>
+
+<dt><b>high</b></dt>
+<dd> Enable only "HIGH" grade OpenSSL ciphers. This setting may
+be appropriate when all mandatory TLS destinations (e.g. when all
+mail is routed to a suitably capable <a href="postconf.5.html#relayhost">relayhost</a>) support at least one
+"HIGH" grade cipher. The underlying cipherlist is specified via the
+<a href="postconf.5.html#tls_high_cipherlist">tls_high_cipherlist</a> configuration parameter, which you are strongly
+encouraged to not change. </dd>
+
+<dt><b>null</b></dt>
+<dd> Enable only the "NULL" OpenSSL ciphers, these provide authentication
+without encryption. This setting is only appropriate in the rare case
+that all servers are prepared to use NULL ciphers (not normally enabled
+in TLS servers). A plausible use-case is an LMTP server listening on a
+UNIX-domain socket that is configured to support "NULL" ciphers. The
+underlying cipherlist is specified via the <a href="postconf.5.html#tls_null_cipherlist">tls_null_cipherlist</a>
+configuration parameter, which you are strongly encouraged to not
+change. </dd>
+
+</dl>
+
+<p> The underlying cipherlists for grades other than "null" include
+anonymous ciphers, but these are automatically filtered out if the
+Postfix SMTP client is configured to verify server certificates.
+You are very unlikely to need to take any steps to exclude anonymous
+ciphers, they are excluded automatically as necessary. If you must
+exclude anonymous ciphers at the "may" or "encrypt" security levels,
+when the Postfix SMTP client does not need or use peer certificates, set
+"<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> = aNULL". To exclude anonymous ciphers only when
+TLS is enforced, set "<a href="postconf.5.html#smtp_tls_mandatory_exclude_ciphers">smtp_tls_mandatory_exclude_ciphers</a> = aNULL". </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_mandatory_exclude_ciphers">smtp_tls_mandatory_exclude_ciphers</a>
+(default: empty)</b></DT><DD>
+
+<p> Additional list of ciphers or cipher types to exclude from the
+Postfix SMTP client cipher list at mandatory TLS security levels. This list
+works in addition to the exclusions listed with <a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a>
+(see there for syntax details). </p>
+
+<p> Starting with Postfix 2.6, the mandatory cipher exclusions can be
+specified on a per-destination basis via the TLS policy "exclude"
+attribute. See <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> for notes and examples. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a>
+(default: !SSLv2, !SSLv3)</b></DT><DD>
+
+<p> List of SSL/TLS protocols that the Postfix SMTP client will use with
+mandatory TLS encryption. In <a href="postconf.5.html">main.cf</a> the values are separated by
+whitespace, commas or colons. In the policy table "protocols" attribute
+(see <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>) the only valid separator is colon. An
+empty value means allow all protocols. The valid protocol names, (see
+<b>SSL_get_version(3)</b>), are "SSLv2", "SSLv3" and "TLSv1". The
+default value is "!SSLv2, !SSLv3" for Postfix releases after the
+middle of 2015, "!SSLv2" for older releases. </p>
+
+<p> With Postfix &ge; 2.5 the parameter syntax was expanded to support
+protocol exclusions. One can explicitly exclude "SSLv2" by setting
+"<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = !SSLv2". To exclude both "SSLv2" and
+"SSLv3" set "<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = !SSLv2, !SSLv3". Listing
+the protocols to include, rather than protocols to exclude, is
+supported, but not recommended. The exclusion form more closely
+matches the underlying OpenSSL interface semantics.
+</p>
+
+<p> The range of protocols advertised by an SSL/TLS client must be
+contiguous. When a protocol version is enabled, disabling any
+higher version implicitly disables all versions above that higher version.
+Thus, for example (assuming the OpenSSL library supports both SSLv2
+and SSLv3):
+</p>
+<blockquote>
+<pre>
+<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = !SSLv2, !TLSv1
+</pre>
+</blockquote>
+<p> also disables any protocols version higher than TLSv1 leaving
+only "SSLv3" enabled. </p>
+
+<p> Note: As of OpenSSL 1.0.1 two new protocols are defined, "TLSv1.1"
+and "TLSv1.2". When Postfix &le; 2.5 is linked against OpenSSL 1.0.1
+or later, these, or any other new protocol versions, cannot be
+disabled except by also disabling "TLSv1" (typically leaving just
+"SSLv3"). The latest patch levels of Postfix &ge; 2.6, and all
+versions of Postfix &ge; 2.10 can explicitly disable support for
+"TLSv1.1" or "TLSv1.2". </p>
+
+<p> OpenSSL 1.1.1 introduces support for "TLSv1.3". With Postfix
+&ge; 3.4 (or patch releases &ge; 3.0.14, 3.1.10, 3.2.7 and 3.3.2)
+this can be disabled, if need be, via "!TLSv1.3". </p>
+
+<p> At the <a href="TLS_README.html#client_tls_dane">dane</a> and
+<a href="TLS_README.html#client_tls_dane">dane-only</a> security
+levels, when usable TLSA records are obtained for the remote SMTP
+server, the Postfix SMTP client is obligated to include the SNI TLS
+extension in its SSL client hello message. This may help the remote
+SMTP server live up to its promise to provide a certificate that
+matches its TLSA records. Since TLS extensions require TLS 1.0 or
+later, the Postfix SMTP client must disable "SSLv2" and "SSLv3" when
+SNI is required. If you use "dane" or "dane-only" do not disable
+TLSv1, except perhaps via the policy table for destinations which
+you are sure will support "TLSv1.1" or "TLSv1.2". </p>
+
+<p> See the documentation of the <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> parameter and
+<a href="TLS_README.html">TLS_README</a> for more information about security levels. </p>
+
+<p> Example: </p>
+
+<pre>
+# Preferred syntax with Postfix &ge; 2.5:
+<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = !SSLv2, !SSLv3
+# Legacy syntax:
+<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = TLSv1
+</pre>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_note_starttls_offer">smtp_tls_note_starttls_offer</a>
+(default: no)</b></DT><DD>
+
+<p> Log the hostname of a remote SMTP server that offers STARTTLS,
+when TLS is not already enabled for that server. </p>
+
+<p> The logfile record looks like: </p>
+
+<pre>
+postfix/smtp[pid]: Host offered STARTTLS: [name.of.host]
+</pre>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_per_site">smtp_tls_per_site</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional lookup tables with the Postfix SMTP client TLS usage
+policy by next-hop destination and by remote SMTP server hostname.
+When both lookups succeed, the more specific per-site policy (NONE,
+MUST, etc) overrides the less specific one (MAY), and the more secure
+per-site policy (MUST, etc) overrides the less secure one (NONE).
+With Postfix 2.3 and later <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> is strongly discouraged:
+use <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> instead. </p>
+
+<p> Use of the bare hostname as the per-site table lookup key is
+discouraged. Always use the full destination nexthop (enclosed in
+[] with a possible ":port" suffix). A recipient domain or MX-enabled
+transport next-hop with no port suffix may look like a bare hostname,
+but is still a suitable <i>destination</i>. </p>
+
+<p> Specify a next-hop destination or server hostname on the left-hand
+side; no wildcards are allowed. The next-hop destination is either
+the recipient domain, or the destination specified with a <a href="transport.5.html">transport(5)</a>
+table, the <a href="postconf.5.html#relayhost">relayhost</a> parameter, or the <a href="postconf.5.html#relay_transport">relay_transport</a> parameter.
+On the right hand side specify one of the following keywords: </p>
+
+<dl>
+
+<dt> NONE </dt> <dd> Don't use TLS at all. This overrides a less
+specific <b>MAY</b> lookup result from the alternate host or next-hop
+lookup key, and overrides the global <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a>, <a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a>,
+and <a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a> settings. </dd>
+
+<dt> MAY </dt> <dd> Try to use TLS if the server announces support,
+otherwise use the unencrypted connection. This has less precedence
+than a more specific result (including <b>NONE</b>) from the alternate
+host or next-hop lookup key, and has less precedence than the more
+specific global "<a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a> = yes" or "<a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a>
+= yes". </dd>
+
+<dt> MUST_NOPEERMATCH </dt> <dd> Require TLS encryption, but do not
+require that the remote SMTP server hostname matches the information
+in the remote SMTP server certificate, or that the server certificate
+was issued by a trusted CA. This overrides a less secure <b>NONE</b>
+or a less specific <b>MAY</b> lookup result from the alternate host
+or next-hop lookup key, and overrides the global <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a>,
+<a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a> and <a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a> settings. </dd>
+
+<dt> MUST </dt> <dd> Require TLS encryption, require that the remote
+SMTP server hostname matches the information in the remote SMTP
+server certificate, and require that the remote SMTP server certificate
+was issued by a trusted CA. This overrides a less secure <b>NONE</b>
+and <b>MUST_NOPEERMATCH</b> or a less specific <b>MAY</b> lookup
+result from the alternate host or next-hop lookup key, and overrides
+the global <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a>, <a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a> and <a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a>
+settings. </dd>
+
+</dl>
+
+<p> The above keywords correspond to the "none", "may", "encrypt" and
+"verify" security levels for the new <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> parameter
+introduced in Postfix 2.3. Starting with Postfix 2.3, and independently
+of how the policy is specified, the <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> and
+<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> parameters apply when TLS encryption
+is mandatory. Connections for which encryption is optional typically
+enable all "export" grade and better ciphers (see <a href="postconf.5.html#smtp_tls_ciphers">smtp_tls_ciphers</a>
+and <a href="postconf.5.html#smtp_tls_protocols">smtp_tls_protocols</a>). </p>
+
+<p> As long as no secure DNS lookup mechanism is available, false
+hostnames in MX or CNAME responses can change the server hostname
+that Postfix uses for TLS policy lookup and server certificate
+verification. Even with a perfect match between the server hostname and
+the server certificate, there is no guarantee that Postfix is connected
+to the right server. See <a href="TLS_README.html">TLS_README</a> (Closing a DNS loophole with obsolete
+per-site TLS policies) for a possible work-around. </p>
+
+<p> This feature is available in Postfix 2.2 and later. With
+Postfix 2.3 and later use <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> instead. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_policy_maps">smtp_tls_policy_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional lookup tables with the Postfix SMTP client TLS security
+policy by next-hop destination; when a non-empty value is specified,
+this overrides the obsolete <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> parameter. See
+<a href="TLS_README.html">TLS_README</a> for a more detailed discussion of TLS security levels.
+</p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p> The TLS policy table is indexed by the full next-hop destination,
+which is either the recipient domain, or the verbatim next-hop
+specified in the transport table, $<a href="postconf.5.html#local_transport">local_transport</a>, $<a href="postconf.5.html#virtual_transport">virtual_transport</a>,
+$<a href="postconf.5.html#relay_transport">relay_transport</a> or $<a href="postconf.5.html#default_transport">default_transport</a>. This includes any enclosing
+square brackets and any non-default destination server port suffix. The
+LMTP socket type prefix (inet: or unix:) is not included in the lookup
+key. </p>
+
+<p> Only the next-hop domain, or $<a href="postconf.5.html#myhostname">myhostname</a> with LMTP over UNIX-domain
+sockets, is used as the nexthop name for certificate verification. The
+port and any enclosing square brackets are used in the table lookup key,
+but are not used for server name verification. </p>
+
+<p> When the lookup key is a domain name without enclosing square brackets
+or any <i>:port</i> suffix (typically the recipient domain), and the full
+domain is not found in the table, just as with the <a href="transport.5.html">transport(5)</a> table,
+the parent domain starting with a leading "." is matched recursively. This
+allows one to specify a security policy for a recipient domain and all
+its sub-domains. </p>
+
+<p> The lookup result is a security level, followed by an optional list
+of whitespace and/or comma separated name=value attributes that override
+related <a href="postconf.5.html">main.cf</a> settings. The TLS security levels in order of increasing
+security are: </p>
+
+<dl>
+
+<dt><b><a href="TLS_README.html#client_tls_none">none</a></b></dt>
+<dd>No TLS. No additional attributes are supported at this level. </dd>
+
+<dt><b><a href="TLS_README.html#client_tls_may">may</a></b></dt>
+<dd>Opportunistic TLS. Since sending in the clear is acceptable,
+demanding stronger than default TLS security merely reduces
+interoperability. The optional "ciphers", "exclude", and "protocols"
+attributes (available for opportunistic TLS with Postfix &ge; 2.6)
+and "connection_reuse" attribute (Postfix &ge; 3.4) override the
+"<a href="postconf.5.html#smtp_tls_ciphers">smtp_tls_ciphers</a>", "<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a>", "<a href="postconf.5.html#smtp_tls_protocols">smtp_tls_protocols</a>",
+and
+"<a href="postconf.5.html#smtp_tls_connection_reuse">smtp_tls_connection_reuse</a>" configuration parameters. When opportunistic
+TLS handshakes fail, Postfix retries the connection with TLS disabled.
+This allows mail delivery to sites with non-interoperable TLS
+implementations.</dd>
+
+<dt><b><a href="TLS_README.html#client_tls_encrypt">encrypt</a></b></dt>
+<dd>Mandatory TLS encryption. At this level
+and higher, the optional "protocols" attribute overrides the <a href="postconf.5.html">main.cf</a>
+<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> parameter, the optional "ciphers" attribute
+overrides the <a href="postconf.5.html">main.cf</a> <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> parameter, the
+optional "exclude" attribute (Postfix &ge; 2.6) overrides the <a href="postconf.5.html">main.cf</a>
+<a href="postconf.5.html#smtp_tls_mandatory_exclude_ciphers">smtp_tls_mandatory_exclude_ciphers</a> parameter, and the optional
+"connection_reuse" attribute (Postfix &ge; 3.4) overrides the
+<a href="postconf.5.html">main.cf</a> <a href="postconf.5.html#smtp_tls_connection_reuse">smtp_tls_connection_reuse</a> parameter. In the policy table,
+multiple protocols or excluded ciphers must be separated by colons,
+as attribute values may not contain whitespace or commas. </dd>
+
+<dt><b><a href="TLS_README.html#client_tls_dane">dane</a></b></dt>
+<dd>Opportunistic DANE TLS. The TLS policy for the destination is
+obtained via TLSA records in DNSSEC. If no TLSA records are found,
+the effective security level used is <a
+href="TLS_README.html#client_tls_may">may</a>. If TLSA records are
+found, but none are usable, the effective security level is <a
+href="TLS_README.html#client_tls_encrypt">encrypt</a>. When usable
+TLSA records are obtained for the remote SMTP server, the
+server certificate must match the TLSA records. <a href="http://tools.ietf.org/html/rfc7672">RFC 7672</a> (DANE)
+TLS authentication and DNSSEC support is available with Postfix
+2.11 and later. The optional "connection_reuse" attribute (Postfix
+&ge; 3.4) overrides the <a href="postconf.5.html">main.cf</a> <a href="postconf.5.html#smtp_tls_connection_reuse">smtp_tls_connection_reuse</a> parameter.
+</dd>
+
+<dt><b><a href="TLS_README.html#client_tls_dane">dane-only</a></b></dt>
+<dd>Mandatory DANE TLS. The TLS policy for the destination is
+obtained via TLSA records in DNSSEC. If no TLSA records are found,
+or none are usable, no connection is made to the server. When
+usable TLSA records are obtained for the remote SMTP server, the
+server certificate must match the TLSA records. <a href="http://tools.ietf.org/html/rfc7672">RFC 7672</a> (DANE) TLS
+authentication and DNSSEC support is available with Postfix 2.11
+and later. The optional "connection_reuse" attribute (Postfix &ge;
+3.4) overrides the <a href="postconf.5.html">main.cf</a> <a href="postconf.5.html#smtp_tls_connection_reuse">smtp_tls_connection_reuse</a> parameter.
+</dd>
+
+<dt><b><a href="TLS_README.html#client_tls_fprint">fingerprint</a></b></dt>
+<dd>Certificate fingerprint
+verification. Available with Postfix 2.5 and later. At this security
+level, there are no trusted Certification Authorities. The certificate
+trust chain, expiration date, ... are not checked. Instead,
+the optional <b>match</b> attribute, or else the <a href="postconf.5.html">main.cf</a>
+<b><a href="postconf.5.html#smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a></b> parameter, lists the certificate
+fingerprints or the public key fingerprint (Postfix 2.9 and later)
+of the valid server certificate. The digest
+algorithm used to calculate the fingerprint is selected by the
+<b><a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a></b> parameter. Multiple fingerprints can
+be combined with a "|" delimiter in a single match attribute, or multiple
+match attributes can be employed. The ":" character is not used as a
+delimiter as it occurs between each pair of fingerprint (hexadecimal)
+digits. The optional "connection_reuse" attribute (Postfix &ge; 3.4)
+overrides the <a href="postconf.5.html">main.cf</a> <a href="postconf.5.html#smtp_tls_connection_reuse">smtp_tls_connection_reuse</a> parameter. </dd>
+
+<dt><b><a href="TLS_README.html#client_tls_verify">verify</a></b></dt>
+<dd>Mandatory TLS verification. At this security
+level, DNS MX lookups are trusted to be secure enough, and the name
+verified in the server certificate is usually obtained indirectly via
+unauthenticated DNS MX lookups. The optional "match" attribute overrides
+the <a href="postconf.5.html">main.cf</a> <a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a> parameter. In the policy table,
+multiple match patterns and strategies must be separated by colons.
+In practice explicit control over matching is more common with the
+"secure" policy, described below. The optional "connection_reuse"
+attribute (Postfix &ge; 3.4) overrides the <a href="postconf.5.html">main.cf</a>
+<a href="postconf.5.html#smtp_tls_connection_reuse">smtp_tls_connection_reuse</a> parameter. </dd>
+
+<dt><b><a href="TLS_README.html#client_tls_secure">secure</a></b></dt>
+<dd>Secure-channel TLS. At this security level, DNS
+MX lookups, though potentially used to determine the candidate next-hop
+gateway IP addresses, are <b>not</b> trusted to be secure enough for TLS
+peername verification. Instead, the default name verified in the server
+certificate is obtained directly from the next-hop, or is explicitly
+specified via the optional <b>match</b> attribute which overrides the
+<a href="postconf.5.html">main.cf</a> <a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a> parameter. In the policy table,
+multiple match patterns and strategies must be separated by colons.
+The match attribute is most useful when multiple domains are supported by
+common server, the policy entries for additional domains specify matching
+rules for the primary domain certificate. While transport table overrides
+routing the secondary domains to the primary nexthop also allow secure
+verification, they risk delivery to the wrong destination when domains
+change hands or are re-assigned to new gateways. With the "match"
+attribute approach, routing is not perturbed, and mail is deferred if
+verification of a new MX host fails. The optional "connection_reuse"
+attribute (Postfix &ge; 3.4) overrides the <a href="postconf.5.html">main.cf</a>
+<a href="postconf.5.html#smtp_tls_connection_reuse">smtp_tls_connection_reuse</a> parameter. </dd>
+
+</dl>
+
+<p>
+Example:
+</p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/tls_policy
+ # Postfix 2.5 and later
+ <a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a> = md5
+</pre>
+
+<pre>
+/etc/postfix/tls_policy:
+ example.edu none
+ example.mil may
+ example.gov encrypt protocols=TLSv1
+ example.com verify ciphers=high
+ example.net secure
+ .example.net secure match=.example.net:example.net
+ [mail.example.org]:587 secure match=nexthop
+ # Postfix 2.5 and later
+ [thumb.example.org] fingerprint
+ match=EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35
+ match=3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
+</pre>
+
+<p> <b>Note:</b> The <b>hostname</b> strategy if listed in a non-default
+setting of <a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a> or in the <b>match</b> attribute
+in the policy table can render the <b>secure</b> level vulnerable to
+DNS forgery. Do not use the <b>hostname</b> strategy for secure-channel
+configurations in environments where DNS security is not assured. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_protocols">smtp_tls_protocols</a>
+(default: !SSLv2, !SSLv3)</b></DT><DD>
+
+<p> List of TLS protocols that the Postfix SMTP client will exclude or
+include with opportunistic TLS encryption. The default value is
+"!SSLv2, !SSLv3" for Postfix releases after the middle of 2015,
+"!SSLv2" for older releases. Before Postfix 2.6, the Postfix SMTP
+client would use all protocols with opportunistic TLS. </p>
+
+<p> In <a href="postconf.5.html">main.cf</a> the values are separated by whitespace, commas or
+colons. In the policy table (see <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>) the only valid
+separator is colon. An empty value means allow all protocols. The valid
+protocol names, (see <b>SSL_get_version(3)</b>), are "SSLv2", "SSLv3"
+and "TLSv1". </p>
+
+<p> The range of protocols advertised by an SSL/TLS client must be
+contiguous. When a protocol version is enabled, disabling any
+higher version implicitly disables all versions above that higher version.
+Thus, for example (assuming the OpenSSL library supports both SSLv2
+and SSLv3):
+</p>
+<blockquote>
+<pre>
+<a href="postconf.5.html#smtp_tls_protocols">smtp_tls_protocols</a> = !SSLv2, !TLSv1
+</pre>
+</blockquote>
+<p> also disables any protocols version higher than TLSv1 leaving
+only "SSLv3" enabled. </p>
+
+<p> Note: As of OpenSSL 1.0.1 two new protocols are defined, "TLSv1.1"
+and "TLSv1.2". The latest patch levels of Postfix &ge; 2.6, and all
+versions of Postfix &ge; 2.10 can explicitly disable support for
+"TLSv1.1" or "TLSv1.2"</p>
+
+<p> OpenSSL 1.1.1 introduces support for "TLSv1.3". With Postfix
+&ge; 3.4 (or patch releases &ge; 3.0.14, 3.1.10, 3.2.7 and 3.3.2)
+this can be disabled, if need be, via "!TLSv1.3". </p>
+
+<p> To include a protocol list its name, to exclude it, prefix the name
+with a "!" character. To exclude SSLv2 for opportunistic TLS set
+"<a href="postconf.5.html#smtp_tls_protocols">smtp_tls_protocols</a> = !SSLv2". To exclude both "SSLv2" and "SSLv3" set
+"<a href="postconf.5.html#smtp_tls_protocols">smtp_tls_protocols</a> = !SSLv2, !SSLv3". Explicitly listing the protocols to
+include, rather than protocols to exclude, is supported, but not
+recommended. The exclusion form more closely matches the underlying
+OpenSSL interface semantics. </p>
+
+<p> Example: </p>
+<pre>
+# TLSv1 or better:
+<a href="postconf.5.html#smtp_tls_protocols">smtp_tls_protocols</a> = !SSLv2, !SSLv3
+</pre>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_scert_verifydepth">smtp_tls_scert_verifydepth</a>
+(default: 9)</b></DT><DD>
+
+<p> The verification depth for remote SMTP server certificates. A depth
+of 1 is sufficient if the issuing CA is listed in a local CA file. </p>
+
+<p> The default verification depth is 9 (the OpenSSL default) for
+compatibility with earlier Postfix behavior. Prior to Postfix 2.5,
+the default value was 5, but the limit was not actually enforced. If
+you have set this to a lower non-default value, certificates with longer
+trust chains may now fail to verify. Certificate chains with 1 or 2
+CAs are common, deeper chains are more rare and any number between 5
+and 9 should suffice in practice. You can choose a lower number if,
+for example, you trust certificates directly signed by an issuing CA
+but not any CAs it delegates to. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a>
+(default: nexthop, dot-nexthop)</b></DT><DD>
+
+<p> How the Postfix SMTP client verifies the server certificate
+peername for the "secure" TLS security level. In a "secure" TLS policy table
+($<a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>) entry the optional "match" attribute
+overrides this <a href="postconf.5.html">main.cf</a> setting. </p>
+
+<p> This parameter specifies one or more patterns or strategies separated
+by commas, whitespace or colons. In the policy table the only valid
+separator is the colon character. </p>
+
+<p> For a description of the pattern and strategy syntax see the
+<a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a> parameter. The "hostname" strategy should
+be avoided in this context, as in the absence of a secure global DNS, using
+the results of MX lookups in certificate verification is not immune to active
+(man-in-the-middle) attacks on DNS. </p>
+
+<p>
+Sample <a href="postconf.5.html">main.cf</a> setting:
+</p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a> = nexthop
+</pre>
+</blockquote>
+
+<p>
+Sample policy table override:
+</p>
+
+<blockquote>
+<pre>
+example.net secure match=example.com:.example.com
+.example.net secure match=example.com:.example.com
+</pre>
+</blockquote>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_security_level">smtp_tls_security_level</a>
+(default: empty)</b></DT><DD>
+
+<p> The default SMTP TLS security level for the Postfix SMTP client;
+when a non-empty value is specified, this overrides the obsolete
+parameters <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a>, <a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a>, and <a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a>.
+</p>
+
+<p> Specify one of the following security levels: </p>
+
+<dl>
+
+<dt><b><a href="TLS_README.html#client_tls_none">none</a></b></dt>
+<dd> No TLS. TLS will not be used unless enabled for specific
+destinations via <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>. </dd>
+
+<dt><b><a href="TLS_README.html#client_tls_may">may</a></b></dt>
+<dd> Opportunistic TLS. Use TLS if this is supported by the remote
+SMTP server, otherwise use plaintext. Since
+sending in the clear is acceptable, demanding stronger than default TLS
+security merely reduces interoperability.
+The "<a href="postconf.5.html#smtp_tls_ciphers">smtp_tls_ciphers</a>" and "<a href="postconf.5.html#smtp_tls_protocols">smtp_tls_protocols</a>" (Postfix &ge; 2.6)
+configuration parameters provide control over the protocols and
+cipher grade used with opportunistic TLS. With earlier releases the
+opportunistic TLS cipher grade is always "export" and no protocols
+are disabled.
+When TLS handshakes fail, the connection is retried with TLS disabled.
+This allows mail delivery to sites with non-interoperable TLS
+implementations. </dd>
+
+<dt><b><a href="TLS_README.html#client_tls_encrypt">encrypt</a></b></dt>
+<dd>Mandatory TLS encryption. Since a minimum
+level of security is intended, it is reasonable to be specific about
+sufficiently secure protocol versions and ciphers. At this security level
+and higher, the <a href="postconf.5.html">main.cf</a> parameters <a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> and
+<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> specify the TLS protocols and minimum
+cipher grade which the administrator considers secure enough for
+mandatory encrypted sessions. This security level is not an appropriate
+default for systems delivering mail to the Internet. </dd>
+
+<dt><b><a href="TLS_README.html#client_tls_dane">dane</a></b></dt>
+<dd>Opportunistic DANE TLS. At this security level, the TLS policy
+for the destination is obtained via DNSSEC. For TLSA policy to be
+in effect, the destination domain's containing DNS zone must be
+signed and the Postfix SMTP client's operating system must be
+configured to send its DNS queries to a recursive DNS nameserver
+that is able to validate the signed records. Each MX host's DNS
+zone should also be signed, and should publish DANE TLSA (<a href="http://tools.ietf.org/html/rfc7672">RFC 7672</a>)
+records that specify how that MX host's TLS certificate is to be
+verified. TLSA records do not preempt the normal SMTP MX host
+selection algorithm, if some MX hosts support TLSA and others do
+not, TLS security will vary from delivery to delivery. It is up
+to the domain owner to configure their MX hosts and their DNS
+sensibly. To configure the Postfix SMTP client for DNSSEC lookups
+see the documentation for the <a href="postconf.5.html#smtp_dns_support_level">smtp_dns_support_level</a> <a href="postconf.5.html">main.cf</a>
+parameter. When DNSSEC-validated TLSA records are not found the
+effective tls security level is "may". When TLSA records are found,
+but are all unusable the effective security level is "encrypt". For
+purposes of protocol and cipher selection, the "dane" security level
+is treated like a "mandatory" TLS security level, and weak ciphers
+and protocols are disabled. Since DANE authenticates server
+certificates the "aNULL" cipher-suites are transparently excluded
+at this level, no need to configure this manually. <a href="http://tools.ietf.org/html/rfc7672">RFC 7672</a> (DANE)
+TLS authentication is available with Postfix 2.11 and later. </dd>
+
+<dt><b><a href="TLS_README.html#client_tls_dane">dane-only</a></b></dt>
+<dd>Mandatory DANE TLS. This is just like "dane" above, but DANE
+TLSA authentication is required. There is no fallback to "may" or
+"encrypt" when TLSA records are missing or unusable. <a href="http://tools.ietf.org/html/rfc7672">RFC 7672</a>
+(DANE) TLS authentication is available with Postfix 2.11 and later.
+</dd>
+
+<dt><b><a href="TLS_README.html#client_tls_fprint">fingerprint</a></b></dt>
+<dd>Certificate fingerprint verification.
+At this security level, there are no trusted Certification Authorities.
+The certificate trust chain, expiration date, etc., are
+not checked. Instead, the <b><a href="postconf.5.html#smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a></b>
+parameter lists the certificate fingerprint or public key fingerprint
+(Postfix 2.9 and later) of the valid server certificate. The digest
+algorithm used to calculate the fingerprint is selected by the
+<b><a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a></b> parameter. Available with Postfix
+2.5 and later. </dd>
+
+<dt><b><a href="TLS_README.html#client_tls_verify">verify</a></b></dt>
+<dd>Mandatory TLS verification. At this security
+level, DNS MX lookups are trusted to be secure enough, and the name
+verified in the server certificate is usually obtained indirectly
+via unauthenticated DNS MX lookups. The <a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a>
+parameter controls how the server name is verified. In practice explicit
+control over matching is more common at the "secure" level, described
+below. This security level is not an appropriate default for systems
+delivering mail to the Internet. </dd>
+
+<dt><b><a href="TLS_README.html#client_tls_secure">secure</a></b></dt>
+<dd>Secure-channel TLS. At this security level,
+DNS MX lookups, though potentially used to determine the candidate
+next-hop gateway IP addresses, are <b>not</b> trusted to be secure enough
+for TLS peername verification. Instead, the default name verified in
+the server certificate is obtained from the next-hop domain as specified
+in the <a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a> configuration parameter. The default
+matching rule is that a server certificate matches when its name is equal
+to or is a sub-domain of the nexthop domain. This security level is not
+an appropriate default for systems delivering mail to the Internet. </dd>
+
+</dl>
+
+<p>
+Examples:
+</p>
+
+<pre>
+# No TLS. Formerly: <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a>=no and <a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a>=no.
+<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = none
+</pre>
+
+<pre>
+# Opportunistic TLS.
+<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = may
+# Postfix &ge; 2.6:
+# Do not tweak opportunistic ciphers or protocol unless it is essential
+# to do so (if a security vulnerability is found in the SSL library that
+# can be mitigated by disabling a particular protocol or raising the
+# cipher grade from "export" to "low" or "medium").
+<a href="postconf.5.html#smtp_tls_ciphers">smtp_tls_ciphers</a> = export
+<a href="postconf.5.html#smtp_tls_protocols">smtp_tls_protocols</a> = !SSLv2, !SSLv3
+</pre>
+
+<pre>
+# Mandatory (high-grade) TLS encryption.
+<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = encrypt
+<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> = high
+</pre>
+
+<pre>
+# Mandatory TLS verification of hostname or nexthop domain.
+<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = verify
+<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> = high
+<a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a> = hostname, nexthop, dot-nexthop
+</pre>
+
+<pre>
+# Secure channel TLS with exact nexthop name match.
+<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = secure
+<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = TLSv1
+<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> = high
+<a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a> = nexthop
+</pre>
+
+<pre>
+# Certificate fingerprint verification (Postfix &ge; 2.5).
+# The CA-less "fingerprint" security level only scales to a limited
+# number of destinations. As a global default rather than a per-site
+# setting, this is practical when mail for all recipients is sent
+# to a central mail hub.
+<a href="postconf.5.html#relayhost">relayhost</a> = [mailhub.example.com]
+<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = fingerprint
+<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = !SSLv2, !SSLv3
+<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> = high
+<a href="postconf.5.html#smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a> =
+ 3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
+ EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35
+</pre>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_servername">smtp_tls_servername</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional name to send to the remote SMTP server in the TLS Server
+Name Indication (SNI) extension. The SNI extension is always on when
+DANE is used to authenticate the server, and in that case the SNI name
+sent is the one required by <a href="http://tools.ietf.org/html/rfc7672">RFC7672</a> and this parameter is ignored. </p>
+
+<p> Some SMTP servers use the received SNI name to select an appropriate
+certificate chain to present to the client. While this may improve
+interoperability with such servers, it may reduce interoperability with
+other servers that choose to abort the connection when they don't have a
+certificate chain configured for the requested name. Such servers
+should select a default certificate chain and continue the handshake,
+but some may not. Therefore, absent DANE, no SNI name is sent by
+default. </p>
+
+<p> The SNI name must be either a valid DNS hostname, or else one of the
+special values <b>hostname</b> or <b>nexthop</b>, which select either the
+remote hostname or the nexthop domain respectively. DNS names for SNI must be
+in A-label (punycode) form. Invalid DNS names log a configuration error
+warning and mail delivery is deferred. </p>
+
+<p> Except when using a <a href="postconf.5.html#relayhost">relayhost</a> to forward all email, the only
+sensible non-empty <a href="postconf.5.html">main.cf</a> setting for this parameter is
+<b>hostname</b>. Other non-empty values are only practical on a
+per-destination basis via the <b>servername</b> attribute of the Postfix
+TLS <a href="TLS_README.html#client_tls_policy">policy table</a>. When
+in doubt, leave this parameter empty, and configure per-destination SNI
+as needed. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_session_cache_database">smtp_tls_session_cache_database</a>
+(default: empty)</b></DT><DD>
+
+<p> Name of the file containing the optional Postfix SMTP client
+TLS session cache. Specify a database type that supports enumeration,
+such as <b>btree</b> or <b>sdbm</b>; there is no need to support
+concurrent access. The file is created if it does not exist. The <a href="smtp.8.html">smtp(8)</a>
+daemon does not use this parameter directly, rather the cache is
+implemented indirectly in the <a href="tlsmgr.8.html">tlsmgr(8)</a> daemon. This means that
+per-smtp-instance <a href="master.5.html">master.cf</a> overrides of this parameter are not effective.
+Note, that each of the cache databases supported by <a href="tlsmgr.8.html">tlsmgr(8)</a> daemon:
+$<a href="postconf.5.html#smtpd_tls_session_cache_database">smtpd_tls_session_cache_database</a>, $<a href="postconf.5.html#smtp_tls_session_cache_database">smtp_tls_session_cache_database</a>
+(and with Postfix 2.3 and later $<a href="postconf.5.html#lmtp_tls_session_cache_database">lmtp_tls_session_cache_database</a>), needs to
+be stored separately. It is not at this time possible to store multiple
+caches in a single database. </p>
+
+<p> Note: <b>dbm</b> databases are not suitable. TLS
+session objects are too large. </p>
+
+<p> As of version 2.5, Postfix no longer uses root privileges when
+opening this file. The file should now be stored under the Postfix-owned
+<a href="postconf.5.html#data_directory">data_directory</a>. As a migration aid, an attempt to open the file
+under a non-Postfix directory is redirected to the Postfix-owned
+<a href="postconf.5.html#data_directory">data_directory</a>, and a warning is logged. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtp_tls_session_cache_database">smtp_tls_session_cache_database</a> = <a href="DATABASE_README.html#types">btree</a>:/var/lib/postfix/smtp_scache
+</pre>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_session_cache_timeout">smtp_tls_session_cache_timeout</a>
+(default: 3600s)</b></DT><DD>
+
+<p> The expiration time of Postfix SMTP client TLS session cache
+information. A cache cleanup is performed periodically
+every $<a href="postconf.5.html#smtp_tls_session_cache_timeout">smtp_tls_session_cache_timeout</a> seconds. As with
+$<a href="postconf.5.html#smtp_tls_session_cache_database">smtp_tls_session_cache_database</a>, this parameter is implemented in the
+<a href="tlsmgr.8.html">tlsmgr(8)</a> daemon and therefore per-smtp-instance <a href="master.5.html">master.cf</a> overrides
+are not possible. </p>
+
+<p> As of Postfix 2.11 this setting cannot exceed 100 days. If set
+&le; 0, session caching is disabled. If set to a positive value
+less than 2 minutes, the minimum value of 2 minutes is used instead. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_trust_anchor_file">smtp_tls_trust_anchor_file</a>
+(default: empty)</b></DT><DD>
+
+<p> Zero or more PEM-format files with trust-anchor certificates
+and/or public keys. If the parameter is not empty the root CAs in
+CAfile and CApath are no longer trusted. Rather, the Postfix SMTP
+client will only trust certificate-chains signed by one of the
+trust-anchors contained in the chosen files. The specified
+trust-anchor certificates and public keys are not subject to
+expiration, and need not be (self-signed) root CAs. They may, if
+desired, be intermediate certificates. Therefore, these certificates
+also may be found "in the middle" of the trust chain presented by
+the remote SMTP server, and any untrusted issuing parent certificates
+will be ignored. Specify a list of pathnames separated by comma
+or whitespace. </p>
+
+<p> Whether specified in <a href="postconf.5.html">main.cf</a>, or on a per-destination basis,
+the trust-anchor PEM file must be accessible to the Postfix SMTP
+client in the chroot jail if applicable. The trust-anchor file
+should contain only certificates and public keys, no private key
+material, and must be readable by the non-privileged $<a href="postconf.5.html#mail_owner">mail_owner</a>
+user. This allows destinations to be bound to a set of specific
+CAs or public keys without trusting the same CAs for all destinations.
+</p>
+
+<p> The <a href="postconf.5.html">main.cf</a> parameter supports single-purpose Postfix installations
+that send mail to a fixed set of SMTP peers. At most sites, if
+trust-anchor files are used at all, they will be specified on a
+per-destination basis via the "tafile" attribute of the "verify"
+and "secure" levels in <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>. </p>
+
+<p> The underlying mechanism is in support of <a href="http://tools.ietf.org/html/rfc7672">RFC 7672</a> (DANE TLSA),
+which defines mechanisms for an SMTP client MTA to securely determine
+server TLS certificates via DNS. </p>
+
+<p> If you want your trust anchors to be public keys, with OpenSSL
+you can extract a single PEM public key from a PEM X.509 file
+containing a single certificate, as follows: </p>
+
+<blockquote>
+<pre>
+$ openssl x509 -in cert.pem -out ta-key.pem -noout -pubkey
+</pre>
+</blockquote>
+
+<p> This feature is available in Postfix 2.11 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a>
+(default: hostname)</b></DT><DD>
+
+<p> How the Postfix SMTP client verifies the server certificate
+peername for the
+"verify" TLS security level. In a "verify" TLS policy table
+($<a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>) entry the optional "match" attribute
+overrides this <a href="postconf.5.html">main.cf</a> setting. </p>
+
+<p> This parameter specifies one or more patterns or strategies separated
+by commas, whitespace or colons. In the policy table the only valid
+separator is the colon character. </p>
+
+<p> Patterns specify domain names, or domain name suffixes: </p>
+
+<dl>
+
+<dt><i>example.com</i></dt> <dd> Match the <i>example.com</i> domain,
+i.e. one of the names the server certificate must be <i>example.com</i>,
+upper and lower case distinctions are ignored. </dd>
+
+<dt><i>.example.com</i></dt>
+<dd> Match subdomains of the <i>example.com</i> domain, i.e. match
+a name in the server certificate that consists of a non-zero number of
+labels followed by a <i>.example.com</i> suffix. Case distinctions are
+ignored.</dd>
+
+</dl>
+
+<p> Strategies specify a transformation from the next-hop domain
+to the expected name in the server certificate: </p>
+
+<dl>
+
+<dt>nexthop</dt>
+<dd> Match against the next-hop domain, which is either the recipient
+domain, or the transport next-hop configured for the domain stripped of
+any optional socket type prefix, enclosing square brackets and trailing
+port. When MX lookups are not suppressed, this is the original nexthop
+domain prior to the MX lookup, not the result of the MX lookup. For
+LMTP delivery via UNIX-domain sockets, the verified next-hop name is
+$<a href="postconf.5.html#myhostname">myhostname</a>. This strategy is suitable for use with the "secure"
+policy. Case is ignored.</dd>
+
+<dt>dot-nexthop</dt>
+<dd> As above, but match server certificate names that are subdomains
+of the next-hop domain. Case is ignored.</dd>
+
+<dt>hostname</dt> <dd> Match against the hostname of the server, often
+obtained via an unauthenticated DNS MX lookup. For LMTP delivery via
+UNIX-domain sockets, the verified name is $<a href="postconf.5.html#myhostname">myhostname</a>. This matches
+the verification strategy of the "MUST" keyword in the obsolete
+<a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> table, and is suitable for use with the "verify"
+security level. When the next-hop name is enclosed in square brackets
+to suppress MX lookups, the "hostname" strategy is the same as the
+"nexthop" strategy. Case is ignored.</dd>
+
+</dl>
+
+<p>
+Sample <a href="postconf.5.html">main.cf</a> setting:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a> = hostname, nexthop, dot-nexthop
+</pre>
+
+<p>
+Sample policy table override:
+</p>
+
+<pre>
+example.com verify match=hostname:nexthop
+.example.com verify match=example.com:.example.com:hostname
+</pre>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_tls_wrappermode">smtp_tls_wrappermode</a>
+(default: no)</b></DT><DD>
+
+<p> Request that the Postfix SMTP client connects using the
+legacy SMTPS protocol instead of using the STARTTLS command. </p>
+
+<p> This mode requires "<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = encrypt" or
+stronger. </p>
+
+<p> Example: deliver all remote mail via a provider's server
+"mail.example.com". </p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ # Client-side SMTPS requires "encrypt" or stronger.
+ <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = encrypt
+ <a href="postconf.5.html#smtp_tls_wrappermode">smtp_tls_wrappermode</a> = yes
+ # The [] suppress MX lookups.
+ <a href="postconf.5.html#relayhost">relayhost</a> = [mail.example.com]:465
+</pre>
+
+<p> More examples are in <a href="TLS_README.html">TLS_README</a>, including examples for older
+Postfix versions. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_use_tls">smtp_use_tls</a>
+(default: no)</b></DT><DD>
+
+<p> Opportunistic mode: use TLS when a remote SMTP server announces
+STARTTLS support, otherwise send the mail in the clear. Beware:
+some SMTP servers offer STARTTLS even if it is not configured. With
+Postfix &lt; 2.3, if the TLS handshake fails, and no other server is
+available, delivery is deferred and mail stays in the queue. If this
+is a concern for you, use the <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> feature instead. </p>
+
+<p> This feature is available in Postfix 2.2 and later. With
+Postfix 2.3 and later use <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> instead. </p>
+
+
+</DD>
+
+<DT><b><a name="smtp_xforward_timeout">smtp_xforward_timeout</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The Postfix SMTP client time limit for sending the XFORWARD command,
+and for receiving the remote SMTP server response.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_authorized_verp_clients">smtpd_authorized_verp_clients</a>
+(default: $<a href="postconf.5.html#authorized_verp_clients">authorized_verp_clients</a>)</b></DT><DD>
+
+<p> What remote SMTP clients are allowed to specify the XVERP command.
+This command requests that mail be delivered one recipient at a
+time with a per recipient return address. </p>
+
+<p> By default, no clients are allowed to specify XVERP. </p>
+
+<p> This parameter was renamed with Postfix version 2.1. The default value
+is backwards compatible with Postfix version 2.0. </p>
+
+<p> Specify a list of network/netmask patterns, separated by commas
+and/or whitespace. The mask specifies the number of bits in the
+network part of a host address. You can also specify hostnames or
+.domain names (the initial dot causes the domain to match any name
+below it), "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns. A "/file/name"
+pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table
+is matched when a table entry matches a lookup string (the lookup
+result is ignored). Continue long lines by starting the next line
+with whitespace. Specify "!pattern" to exclude an address or network
+block from the list. The form "!/file/name" is supported only in
+Postfix version 2.4 and later. </p>
+
+<p> Note: IP version 6 address information must be specified inside
+<tt>[]</tt> in the <a href="postconf.5.html#smtpd_authorized_verp_clients">smtpd_authorized_verp_clients</a> value, and in
+files specified with "/file/name". IP version 6 addresses contain
+the ":" character, and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>"
+pattern. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_authorized_xclient_hosts">smtpd_authorized_xclient_hosts</a>
+(default: empty)</b></DT><DD>
+
+<p>
+What remote SMTP clients are allowed to use the XCLIENT feature. This
+command overrides remote SMTP client information that is used for access
+control. Typical use is for SMTP-based content filters, fetchmail-like
+programs, or SMTP server access rule testing. See the <a href="XCLIENT_README.html">XCLIENT_README</a>
+document for details.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+<p>
+By default, no clients are allowed to specify XCLIENT.
+</p>
+
+<p>
+Specify a list of network/netmask patterns, separated by commas
+and/or whitespace. The mask specifies the number of bits in the
+network part of a host address. You can also specify hostnames or
+.domain names (the initial dot causes the domain to match any name
+below it), "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns. A "/file/name"
+pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table
+is matched when a table entry matches a lookup string (the lookup
+result is ignored). Continue long lines by starting the next line
+with whitespace. Specify "!pattern" to exclude an address or network
+block from the list. The form "!/file/name" is supported only in
+Postfix version 2.4 and later. </p>
+
+<p> Note: IP version 6 address information must be specified inside
+<tt>[]</tt> in the <a href="postconf.5.html#smtpd_authorized_xclient_hosts">smtpd_authorized_xclient_hosts</a> value, and in
+files specified with "/file/name". IP version 6 addresses contain
+the ":" character, and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>"
+pattern. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_authorized_xforward_hosts">smtpd_authorized_xforward_hosts</a>
+(default: empty)</b></DT><DD>
+
+<p>
+What remote SMTP clients are allowed to use the XFORWARD feature. This
+command forwards information that is used to improve logging after
+SMTP-based content filters. See the <a href="XFORWARD_README.html">XFORWARD_README</a> document for
+details.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+<p>
+By default, no clients are allowed to specify XFORWARD.
+</p>
+
+<p>
+Specify a list of network/netmask patterns, separated by commas
+and/or whitespace. The mask specifies the number of bits in the
+network part of a host address. You can also specify hostnames or
+.domain names (the initial dot causes the domain to match any name
+below it), "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns. A "/file/name"
+pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table
+is matched when a table entry matches a lookup string (the lookup
+result is ignored). Continue long lines by starting the next line
+with whitespace. Specify "!pattern" to exclude an address or network
+block from the list. The form "!/file/name" is supported only in
+Postfix version 2.4 and later. </p>
+
+<p> Note: IP version 6 address information must be specified inside
+<tt>[]</tt> in the <a href="postconf.5.html#smtpd_authorized_xforward_hosts">smtpd_authorized_xforward_hosts</a> value, and in
+files specified with "/file/name". IP version 6 addresses contain
+the ":" character, and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>"
+pattern. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_banner">smtpd_banner</a>
+(default: $<a href="postconf.5.html#myhostname">myhostname</a> ESMTP $<a href="postconf.5.html#mail_name">mail_name</a>)</b></DT><DD>
+
+<p>
+The text that follows the 220 status code in the SMTP greeting
+banner. Some people like to see the mail version advertised. By
+default, Postfix shows no version.
+</p>
+
+<p>
+You MUST specify $<a href="postconf.5.html#myhostname">myhostname</a> at the start of the text. This is
+required by the SMTP protocol.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_banner">smtpd_banner</a> = $<a href="postconf.5.html#myhostname">myhostname</a> ESMTP $<a href="postconf.5.html#mail_name">mail_name</a> ($<a href="postconf.5.html#mail_version">mail_version</a>)
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_client_auth_rate_limit">smtpd_client_auth_rate_limit</a>
+(default: 0)</b></DT><DD>
+
+<p>
+The maximal number of AUTH commands that any client is allowed to
+send to this service per time unit, regardless of whether or not
+Postfix actually accepts those commands. The time unit is specified
+with the <a href="postconf.5.html#anvil_rate_time_unit">anvil_rate_time_unit</a> configuration parameter.
+</p>
+
+<p>
+By default, there is no limit on the number AUTH commands that a
+client may send.
+</p>
+
+<p>
+To disable this feature, specify a limit of 0.
+</p>
+
+<p>
+WARNING: The purpose of this feature is to limit abuse. It must
+not be used to regulate legitimate mail traffic.
+</p>
+
+<p>
+This feature is available in Postfix 3.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_client_connection_count_limit">smtpd_client_connection_count_limit</a>
+(default: 50)</b></DT><DD>
+
+<p>
+How many simultaneous connections any client is allowed to
+make to this service. By default, the limit is set to half
+the default process limit value.
+</p>
+
+<p>
+To disable this feature, specify a limit of 0.
+</p>
+
+<p>
+WARNING: The purpose of this feature is to limit abuse. It must
+not be used to regulate legitimate mail traffic.
+</p>
+
+<p>
+This feature is available in Postfix 2.2 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_client_connection_rate_limit">smtpd_client_connection_rate_limit</a>
+(default: 0)</b></DT><DD>
+
+<p>
+The maximal number of connection attempts any client is allowed to
+make to this service per time unit. The time unit is specified
+with the <a href="postconf.5.html#anvil_rate_time_unit">anvil_rate_time_unit</a> configuration parameter.
+</p>
+
+<p>
+By default, a client can make as many connections per time unit as
+Postfix can accept.
+</p>
+
+<p>
+To disable this feature, specify a limit of 0.
+</p>
+
+<p>
+WARNING: The purpose of this feature is to limit abuse. It must
+not be used to regulate legitimate mail traffic.
+</p>
+
+<p>
+This feature is available in Postfix 2.2 and later.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_client_connection_rate_limit">smtpd_client_connection_rate_limit</a> = 1000
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_client_event_limit_exceptions">smtpd_client_event_limit_exceptions</a>
+(default: $<a href="postconf.5.html#mynetworks">mynetworks</a>)</b></DT><DD>
+
+<p>
+Clients that are excluded from smtpd_client_*_count/rate_limit
+restrictions. See the <a href="postconf.5.html#mynetworks">mynetworks</a> parameter
+description for the parameter value syntax.
+</p>
+
+<p>
+By default, clients in trusted networks are excluded. Specify a
+list of network blocks, hostnames or .domain names (the initial
+dot causes the domain to match any name below it).
+</p>
+
+<p> Note: IP version 6 address information must be specified inside
+<tt>[]</tt> in the <a href="postconf.5.html#smtpd_client_event_limit_exceptions">smtpd_client_event_limit_exceptions</a> value, and
+in files specified with "/file/name". IP version 6 addresses
+contain the ":" character, and would otherwise be confused with a
+"<a href="DATABASE_README.html">type:table</a>" pattern. </p>
+
+<p> Pattern matching of domain names is controlled by the presence
+or absence of "<a href="postconf.5.html#smtpd_client_event_limit_exceptions">smtpd_client_event_limit_exceptions</a>" in the
+<a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a> parameter value (postfix 3.0 and
+later). </p>
+
+<p>
+This feature is available in Postfix 2.2 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_client_message_rate_limit">smtpd_client_message_rate_limit</a>
+(default: 0)</b></DT><DD>
+
+<p>
+The maximal number of message delivery requests that any client is
+allowed to make to this service per time unit, regardless of whether
+or not Postfix actually accepts those messages. The time unit is
+specified with the <a href="postconf.5.html#anvil_rate_time_unit">anvil_rate_time_unit</a> configuration parameter.
+</p>
+
+<p>
+By default, a client can send as many message delivery requests
+per time unit as Postfix can accept.
+</p>
+
+<p>
+To disable this feature, specify a limit of 0.
+</p>
+
+<p>
+WARNING: The purpose of this feature is to limit abuse. It must
+not be used to regulate legitimate mail traffic.
+</p>
+
+<p>
+This feature is available in Postfix 2.2 and later.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_client_message_rate_limit">smtpd_client_message_rate_limit</a> = 1000
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_client_new_tls_session_rate_limit">smtpd_client_new_tls_session_rate_limit</a>
+(default: 0)</b></DT><DD>
+
+<p>
+The maximal number of new (i.e., uncached) TLS sessions that a
+remote SMTP client is allowed to negotiate with this service per
+time unit. The time unit is specified with the <a href="postconf.5.html#anvil_rate_time_unit">anvil_rate_time_unit</a>
+configuration parameter.
+</p>
+
+<p>
+By default, a remote SMTP client can negotiate as many new TLS
+sessions per time unit as Postfix can accept.
+</p>
+
+<p>
+To disable this feature, specify a limit of 0. Otherwise, specify
+a limit that is at least the per-client concurrent session limit,
+or else legitimate client sessions may be rejected.
+</p>
+
+<p>
+WARNING: The purpose of this feature is to limit abuse. It must
+not be used to regulate legitimate mail traffic.
+</p>
+
+<p>
+This feature is available in Postfix 2.3 and later.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_client_new_tls_session_rate_limit">smtpd_client_new_tls_session_rate_limit</a> = 100
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_client_port_logging">smtpd_client_port_logging</a>
+(default: no)</b></DT><DD>
+
+<p> Enable logging of the remote SMTP client port in addition to
+the hostname and IP address. The logging format is "host[address]:port".
+</p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_client_recipient_rate_limit">smtpd_client_recipient_rate_limit</a>
+(default: 0)</b></DT><DD>
+
+<p>
+The maximal number of recipient addresses that any client is allowed
+to send to this service per time unit, regardless of whether or not
+Postfix actually accepts those recipients. The time unit is specified
+with the <a href="postconf.5.html#anvil_rate_time_unit">anvil_rate_time_unit</a> configuration parameter.
+</p>
+
+<p>
+By default, a client can send as many recipient addresses per time
+unit as Postfix can accept.
+</p>
+
+<p>
+To disable this feature, specify a limit of 0.
+</p>
+
+<p>
+WARNING: The purpose of this feature is to limit abuse. It must
+not be used to regulate legitimate mail traffic.
+</p>
+
+<p>
+This feature is available in Postfix 2.2 and later.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_client_recipient_rate_limit">smtpd_client_recipient_rate_limit</a> = 1000
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_client_restrictions">smtpd_client_restrictions</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional restrictions that the Postfix SMTP server applies in the
+context of a client connection request.
+See <a href="SMTPD_ACCESS_README.html">SMTPD_ACCESS_README</a>, section "Delayed evaluation of SMTP access
+restriction lists" for a discussion of evaluation context and time.
+</p>
+
+<p>
+The default is to allow all connection requests.
+</p>
+
+<p>
+Specify a list of restrictions, separated by commas and/or whitespace.
+Continue long lines by starting the next line with whitespace.
+Restrictions are applied in the order as specified; the first
+restriction that matches wins.
+</p>
+
+<p>
+The following restrictions are specific to client hostname or
+client network address information.
+</p>
+
+<dl>
+
+<dt><b><a name="check_ccert_access">check_ccert_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd> Use the remote SMTP client certificate fingerprint or the public key
+fingerprint (Postfix 2.9 and later) as lookup key for the specified
+<a href="access.5.html">access(5)</a> database; with Postfix version 2.2, also require that the
+remote SMTP client certificate is verified successfully.
+The fingerprint digest algorithm is configurable via the
+<a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> parameter (hard-coded as md5 prior to
+Postfix version 2.5). This feature is available with Postfix version
+2.2 and later. </dd>
+
+<dt><b><a name="check_client_access">check_client_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified access database for the client hostname,
+parent domains, client IP address, or networks obtained by stripping
+least significant octets. See the <a href="access.5.html">access(5)</a> manual page for details. </dd>
+
+<dt><b><a name="check_client_a_access">check_client_a_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the IP addresses for the
+client hostname, and execute the corresponding action. Note: a result
+of "OK" is not allowed for safety reasons. Instead, use DUNNO in order
+to exclude specific hosts from blacklists. This feature is available
+in Postfix 3.0 and later. </dd>
+
+<dt><b><a name="check_client_mx_access">check_client_mx_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the MX hosts for the
+client hostname, and execute the corresponding action. Note: a result
+of "OK" is not allowed for safety reasons. Instead, use DUNNO in order
+to exclude specific hosts from blacklists. This feature is available
+in Postfix 2.7 and later. </dd>
+
+<dt><b><a name="check_client_ns_access">check_client_ns_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the DNS servers for
+the client hostname, and execute the corresponding action. Note: a
+result of "OK" is not allowed for safety reasons. Instead, use DUNNO
+in order to exclude specific hosts from blacklists. This feature is
+available in Postfix 2.7 and later. </dd>
+
+<dt><b><a name="check_reverse_client_hostname_access">check_reverse_client_hostname_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified access database for the unverified reverse
+client hostname, parent domains, client IP address, or networks
+obtained by stripping least significant octets. See the <a href="access.5.html">access(5)</a>
+manual page for details. Note: a result of "OK" is not allowed for
+safety reasons. Instead, use DUNNO in order to exclude specific
+hosts from blacklists. This feature is available in Postfix 2.6
+and later.</dd>
+
+<dt><b><a name="check_reverse_client_hostname_a_access">check_reverse_client_hostname_a_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the IP addresses for the
+unverified reverse client hostname, and execute the corresponding
+action. Note: a result of "OK" is not allowed for safety reasons.
+Instead, use DUNNO in order to exclude specific hosts from blacklists.
+This feature is available in Postfix 3.0 and later. </dd>
+
+<dt><b><a name="check_reverse_client_hostname_mx_access">check_reverse_client_hostname_mx_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the MX hosts for the
+unverified reverse client hostname, and execute the corresponding
+action. Note: a result of "OK" is not allowed for safety reasons.
+Instead, use DUNNO in order to exclude specific hosts from blacklists.
+This feature is available in Postfix 2.7 and later. </dd>
+
+<dt><b><a name="check_reverse_client_hostname_ns_access">check_reverse_client_hostname_ns_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the DNS servers for
+the unverified reverse client hostname, and execute the corresponding
+action. Note: a result of "OK" is not allowed for safety reasons.
+Instead, use DUNNO in order to exclude specific hosts from blacklists.
+This feature is available in Postfix 2.7 and later. </dd>
+
+<dt><b><a name="check_sasl_access">check_sasl_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd> Use the remote SMTP client SASL user name as lookup key for
+the specified <a href="access.5.html">access(5)</a> database. The lookup key has the form
+"username@domainname" when the <a href="postconf.5.html#smtpd_sasl_local_domain">smtpd_sasl_local_domain</a> parameter
+value is non-empty. Unlike the <a href="postconf.5.html#check_client_access">check_client_access</a> feature,
+<a href="postconf.5.html#check_sasl_access">check_sasl_access</a> does not perform matches of parent domains or IP
+subnet ranges. This feature is available with Postfix version 2.11
+and later. </dd>
+
+<dt><b><a name="permit_inet_interfaces">permit_inet_interfaces</a></b></dt>
+
+<dd>Permit the request when the client IP address matches
+$<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>. </dd>
+
+<dt><b><a name="permit_mynetworks">permit_mynetworks</a></b></dt>
+
+<dd>Permit the request when the client IP address matches any
+network or network address listed in $<a href="postconf.5.html#mynetworks">mynetworks</a>. </dd>
+
+<dt><b><a name="permit_sasl_authenticated">permit_sasl_authenticated</a></b></dt>
+
+<dd> Permit the request when the client is successfully
+authenticated via the <a href="http://tools.ietf.org/html/rfc4954">RFC 4954</a> (AUTH) protocol. </dd>
+
+<dt><b><a name="permit_tls_all_clientcerts">permit_tls_all_clientcerts</a></b></dt>
+
+<dd> Permit the request when the remote SMTP client certificate is
+verified successfully. This option must be used only if a special
+CA issues the certificates and only this CA is listed as trusted
+CA. Otherwise, clients with a third-party certificate would also
+be allowed to relay. Specify "<a href="postconf.5.html#tls_append_default_CA">tls_append_default_CA</a> = no" when the
+trusted CA is specified with <a href="postconf.5.html#smtpd_tls_CAfile">smtpd_tls_CAfile</a> or <a href="postconf.5.html#smtpd_tls_CApath">smtpd_tls_CApath</a>,
+to prevent Postfix from appending the system-supplied default CAs.
+This feature is available with Postfix version 2.2.</dd>
+
+<dt><b><a name="permit_tls_clientcerts">permit_tls_clientcerts</a></b></dt>
+
+<dd>Permit the request when the remote SMTP client certificate
+fingerprint or public key fingerprint (Postfix 2.9 and later) is
+listed in $<a href="postconf.5.html#relay_clientcerts">relay_clientcerts</a>.
+The fingerprint digest algorithm is configurable via the
+<a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> parameter (hard-coded as md5 prior to
+Postfix version 2.5). This feature is available with Postfix version
+2.2. </dd>
+
+<dt><b><a name="reject_rbl_client">reject_rbl_client <i>rbl_domain=d.d.d.d</i></a></b></dt>
+
+<dd>Reject the request when the reversed client network address is
+listed with the A record "<i>d.d.d.d</i>" under <i>rbl_domain</i>
+(Postfix version 2.1 and later only). Each "<i>d</i>" is a number,
+or a pattern inside "[]" that contains one or more ";"-separated
+numbers or number..number ranges (Postfix version 2.8 and later).
+If no "<i>=d.d.d.d</i>" is specified, reject the request when the
+reversed client network address is listed with any A record under
+<i>rbl_domain</i>. <br>
+The <a href="postconf.5.html#maps_rbl_reject_code">maps_rbl_reject_code</a> parameter specifies the response code for
+rejected requests (default: 554), the <a href="postconf.5.html#default_rbl_reply">default_rbl_reply</a> parameter
+specifies the default server reply, and the <a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a> parameter
+specifies tables with server replies indexed by <i>rbl_domain</i>.
+This feature is available in Postfix 2.0 and later. </dd>
+
+<dt><b><a name="permit_dnswl_client">permit_dnswl_client <i>dnswl_domain=d.d.d.d</i></a></b></dt>
+
+<dd>Accept the request when the reversed client network address is
+listed with the A record "<i>d.d.d.d</i>" under <i>dnswl_domain</i>.
+Each "<i>d</i>" is a number, or a pattern inside "[]" that contains
+one or more ";"-separated numbers or number..number ranges.
+If no "<i>=d.d.d.d</i>" is specified, accept the request when the
+reversed client network address is listed with any A record under
+<i>dnswl_domain</i>. <br> For safety, <a href="postconf.5.html#permit_dnswl_client">permit_dnswl_client</a> is silently
+ignored when it would override <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a>. The
+result is DEFER_IF_REJECT when whitelist lookup fails. This feature
+is available in Postfix 2.8 and later. </dd>
+
+<dt><b><a name="reject_rhsbl_client">reject_rhsbl_client <i>rbl_domain=d.d.d.d</i></a></b></dt>
+
+<dd>Reject the request when the client hostname is listed with the
+A record "<i>d.d.d.d</i>" under <i>rbl_domain</i> (Postfix version
+2.1 and later only). Each "<i>d</i>" is a number, or a pattern
+inside "[]" that contains one or more ";"-separated numbers or
+number..number ranges (Postfix version 2.8 and later). If no
+"<i>=d.d.d.d</i>" is specified, reject the request when the client
+hostname is listed with
+any A record under <i>rbl_domain</i>. See the <a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a>
+description above for additional RBL related configuration parameters.
+This feature is available in Postfix 2.0 and later; with Postfix
+version 2.8 and later, <a href="postconf.5.html#reject_rhsbl_reverse_client">reject_rhsbl_reverse_client</a> will usually
+produce better results. </dd>
+
+<dt><b><a name="permit_rhswl_client">permit_rhswl_client <i>rhswl_domain=d.d.d.d</i></a></b></dt>
+
+<dd>Accept the request when the client hostname is listed with the
+A record "<i>d.d.d.d</i>" under <i>rhswl_domain</i>. Each "<i>d</i>"
+is a number, or a pattern inside "[]" that contains one or more
+";"-separated numbers or number..number ranges. If no
+"<i>=d.d.d.d</i>" is specified, accept the request when the client
+hostname is listed with any A record under <i>rhswl_domain</i>.
+<br> Caution: client name whitelisting is fragile, since the client
+name lookup can fail due to temporary outages. Client name
+whitelisting should be used only to reduce false positives in e.g.
+DNS-based blocklists, and not for making access rule exceptions.
+<br> For safety, <a href="postconf.5.html#permit_rhswl_client">permit_rhswl_client</a> is silently ignored when it
+would override <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a>. The result is DEFER_IF_REJECT
+when whitelist lookup fails. This feature is available in Postfix
+2.8 and later. </dd>
+
+<dt><b><a name="reject_rhsbl_reverse_client">reject_rhsbl_reverse_client <i>rbl_domain=d.d.d.d</i></a></b></dt>
+
+<dd>Reject the request when the unverified reverse client hostname
+is listed with the A record "<i>d.d.d.d</i>" under <i>rbl_domain</i>.
+Each "<i>d</i>" is a number, or a pattern inside "[]" that contains
+one or more ";"-separated numbers or number..number ranges.
+If no "<i>=d.d.d.d</i>" is specified, reject the request when the
+unverified reverse client hostname is listed with any A record under
+<i>rbl_domain</i>. See the <a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a> description above for
+additional RBL related configuration parameters. This feature is
+available in Postfix 2.8 and later. </dd>
+
+<dt><b><a name="reject_unknown_client_hostname">reject_unknown_client_hostname</a></b> (with Postfix &lt; 2.3: reject_unknown_client)</dt>
+
+<dd>Reject the request when 1) the client IP address-&gt;name mapping
+fails, or 2) the name-&gt;address mapping fails, or 3) the name-&gt;address
+mapping does not match the client IP address. <br> This is a
+stronger restriction than the <a href="postconf.5.html#reject_unknown_reverse_client_hostname">reject_unknown_reverse_client_hostname</a>
+feature, which triggers only under condition 1) above. <br> The
+<a href="postconf.5.html#unknown_client_reject_code">unknown_client_reject_code</a> parameter specifies the response code
+for rejected requests (default: 450). The reply is always 450 in
+case the address-&gt;name or name-&gt;address lookup failed due to
+a temporary problem. </dd>
+
+<dt><b><a name="reject_unknown_reverse_client_hostname">reject_unknown_reverse_client_hostname</a></b></dt>
+
+<dd>Reject the request when the client IP address has no address-&gt;name
+mapping. <br> This is a weaker restriction than the
+<a href="postconf.5.html#reject_unknown_client_hostname">reject_unknown_client_hostname</a> feature, which requires not only
+that the address-&gt;name and name-&gt;address mappings exist, but
+also that the two mappings reproduce the client IP address. <br>
+The <a href="postconf.5.html#unknown_client_reject_code">unknown_client_reject_code</a> parameter specifies the response
+code for rejected requests (default: 450). The reply is always 450
+in case the address-&gt;name lookup failed due to a temporary
+problem. <br> This feature is available in Postfix 2.3 and
+later. </dd>
+
+</dl>
+
+<p>
+In addition, you can use any of the following <a name="generic">
+generic</a> restrictions. These restrictions are applicable in
+any SMTP command context.
+</p>
+
+<dl>
+
+<dt><b><a name="check_policy_service">check_policy_service <i>servername</i></a></b></dt>
+
+<dd>Query the specified policy server. See the <a href="SMTPD_POLICY_README.html">SMTPD_POLICY_README</a>
+document for details. This feature is available in Postfix 2.1
+and later. </dd>
+
+<dt><b><a name="defer">defer</a></b></dt>
+
+<dd>Defer the request. The client is told to try again later. This
+restriction is useful at the end of a restriction list, to make
+the default policy explicit. <br> The <a href="postconf.5.html#defer_code">defer_code</a> parameter specifies
+the SMTP server reply code (default: 450).</dd>
+
+<dt><b><a name="defer_if_permit">defer_if_permit</a></b></dt>
+
+<dd>Defer the request if some later restriction would result in an
+explicit or implicit PERMIT action. This is useful when a blacklisting
+feature fails due to a temporary problem. This feature is available
+in Postfix version 2.1 and later. </dd>
+
+<dt><b><a name="defer_if_reject">defer_if_reject</a></b></dt>
+
+<dd>Defer the request if some later restriction would result in a
+REJECT action. This is useful when a whitelisting feature fails
+due to a temporary problem. This feature is available in Postfix
+version 2.1 and later. </dd>
+
+<dt><b><a name="permit">permit</a></b></dt>
+
+<dd>Permit the request. This restriction is useful at the end of
+a restriction list, to make the default policy explicit.</dd>
+
+<dt><b><a name="reject_multi_recipient_bounce">reject_multi_recipient_bounce</a></b></dt>
+
+<dd>Reject the request when the envelope sender is the null address,
+and the message has multiple envelope recipients. This usage has
+rare but legitimate applications: under certain conditions,
+multi-recipient mail that was posted with the DSN option NOTIFY=NEVER
+may be forwarded with the null sender address.
+<br> Note: this restriction can only work reliably
+when used in <a href="postconf.5.html#smtpd_data_restrictions">smtpd_data_restrictions</a> or
+<a href="postconf.5.html#smtpd_end_of_data_restrictions">smtpd_end_of_data_restrictions</a>, because the total number of
+recipients is not known at an earlier stage of the SMTP conversation.
+Use at the RCPT stage will only reject the second etc. recipient.
+<br>
+The <a href="postconf.5.html#multi_recipient_bounce_reject_code">multi_recipient_bounce_reject_code</a> parameter specifies the
+response code for rejected requests (default: 550). This feature
+is available in Postfix 2.1 and later. </dd>
+
+<dt><b><a name="reject_plaintext_session">reject_plaintext_session</a></b></dt>
+
+<dd>Reject the request when the connection is not encrypted. This
+restriction should not be used before the client has had a chance
+to negotiate encryption with the AUTH or STARTTLS commands.
+<br>
+The <a href="postconf.5.html#plaintext_reject_code">plaintext_reject_code</a> parameter specifies the response
+code for rejected requests (default: 450). This feature is available
+in Postfix 2.3 and later. </dd>
+
+<dt><b><a name="reject_unauth_pipelining">reject_unauth_pipelining</a></b></dt>
+
+<dd>Reject the request when the client sends SMTP commands ahead
+of time where it is not allowed, or when the client sends SMTP
+commands ahead of time without knowing that Postfix actually supports
+ESMTP command pipelining. This stops mail from bulk mail software
+that improperly uses ESMTP command pipelining in order to speed up
+deliveries.
+<br> With Postfix 2.6 and later, the SMTP server sets a per-session
+flag whenever it detects illegal pipelining, including pipelined
+HELO or EHLO commands. The <a href="postconf.5.html#reject_unauth_pipelining">reject_unauth_pipelining</a> feature simply
+tests whether the flag was set at any point in time during the
+session.
+<br> With older Postfix versions, <a href="postconf.5.html#reject_unauth_pipelining">reject_unauth_pipelining</a> checks
+the current status of the input read queue, and its usage is not
+recommended in contexts other than <a href="postconf.5.html#smtpd_data_restrictions">smtpd_data_restrictions</a>. </dd>
+
+<dt><b><a name="reject">reject</a></b></dt>
+
+<dd>Reject the request. This restriction is useful at the end of
+a restriction list, to make the default policy explicit. The
+<a href="postconf.5.html#reject_code">reject_code</a> configuration parameter specifies the response code for
+rejected requests (default: 554).</dd>
+
+<dt><b><a name="sleep">sleep <i>seconds</i></a></b></dt>
+
+<dd>Pause for the specified number of seconds and proceed with
+the next restriction in the list, if any. This may stop zombie
+mail when used as:
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> =
+ sleep 1, <a href="postconf.5.html#reject_unauth_pipelining">reject_unauth_pipelining</a>
+ <a href="postconf.5.html#smtpd_delay_reject">smtpd_delay_reject</a> = no
+</pre>
+This feature is available in Postfix 2.3. </dd>
+
+<dt><b><a name="warn_if_reject">warn_if_reject</a></b></dt>
+
+<dd> A safety net for testing. When "<a href="postconf.5.html#warn_if_reject">warn_if_reject</a>" is placed
+before a reject-type restriction, access table query, or
+<a href="postconf.5.html#check_policy_service">check_policy_service</a> query, this logs a "reject_warning" message
+instead of rejecting a request (when a reject-type restriction fails
+due to a temporary error, this logs a "reject_warning" message for
+any implicit "<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>" actions that would normally prevent
+mail from being accepted by some later access restriction). This
+feature has no effect on <a href="postconf.5.html#defer_if_reject">defer_if_reject</a> restrictions. </dd>
+
+</dl>
+
+<p>
+Other restrictions that are valid in this context:
+</p>
+
+<ul>
+
+<li> SMTP command specific restrictions that are described under
+the <a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>, <a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a> or
+<a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> parameters. When helo, sender or
+recipient restrictions are listed under <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>,
+they have effect only with "<a href="postconf.5.html#smtpd_delay_reject">smtpd_delay_reject</a> = yes", so that
+$<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> is evaluated at the time of the RCPT TO
+command.
+
+</ul>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, <a href="postconf.5.html#reject_unknown_client_hostname">reject_unknown_client_hostname</a>
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_command_filter">smtpd_command_filter</a>
+(default: empty)</b></DT><DD>
+
+<p> A mechanism to transform commands from remote SMTP clients.
+This is a last-resort tool to work around client commands that break
+interoperability with the Postfix SMTP server. Other uses involve
+fault injection to test Postfix's handling of invalid commands.
+</p>
+
+<p> Specify the name of a "<a href="DATABASE_README.html">type:table</a>" lookup table. The search
+string is the SMTP command as received from the remote SMTP client,
+except that initial whitespace and the trailing &lt;CR&gt;&lt;LF&gt;
+are removed. The result value is executed by the Postfix SMTP
+server. </p>
+
+<p> There is no need to use <a href="postconf.5.html#smtpd_command_filter">smtpd_command_filter</a> for the following
+cases: </p>
+
+<ul>
+
+<li> <p> Use "<a href="postconf.5.html#resolve_numeric_domain">resolve_numeric_domain</a> = yes" to accept
+"<i>user@ipaddress</i>". </p>
+
+<li> <p> Postfix already accepts the correct form
+"<i>user@[ipaddress]</i>". Use <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> or <a href="postconf.5.html#canonical_maps">canonical_maps</a>
+to translate these into domain names if necessary. </p>
+
+<li> <p> Use "<a href="postconf.5.html#strict_rfc821_envelopes">strict_rfc821_envelopes</a> = no" to accept "RCPT TO:&lt;<i>User
+Name &lt;user@example.com&gt;&gt;</i>". Postfix will ignore the "<i>User
+Name</i>" part and deliver to the <i>&lt;user@example.com&gt;</i> address.
+</p>
+
+</ul>
+
+<p> Examples of problems that can be solved with the <a href="postconf.5.html#smtpd_command_filter">smtpd_command_filter</a>
+feature: </p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtpd_command_filter">smtpd_command_filter</a> = <a href="pcre_table.5.html">pcre</a>:/etc/postfix/command_filter
+</pre>
+
+<pre>
+/etc/postfix/command_filter:
+ # Work around clients that send malformed HELO commands.
+ /^HELO\s*$/ HELO domain.invalid
+</pre>
+
+<pre>
+ # Work around clients that send empty lines.
+ /^\s*$/ NOOP
+</pre>
+
+<pre>
+ # Work around clients that send RCPT TO:&lt;'user@domain'&gt;.
+ # WARNING: do not lose the parameters that follow the address.
+ /^(RCPT\s+TO:\s*&lt;)'([^[:space:]]+)'(&gt;.*)/ $1$2$3
+</pre>
+
+<pre>
+ # Append XVERP to MAIL FROM commands to request VERP-style delivery.
+ # See <a href="VERP_README.html">VERP_README</a> for more information on how to use Postfix VERP.
+ /^(MAIL FROM:\s*&lt;listname@example\.com&gt;.*)/ $1 XVERP
+</pre>
+
+<pre>
+ # Bounce-never mail sink. Use <a href="postconf.5.html#notify_classes">notify_classes</a>=bounce,resource,software
+ # to send bounced mail to the postmaster (with message body removed).
+ /^(RCPT\s+TO:\s*&lt;.*&gt;.*)\s+NOTIFY=\S+(.*)/ $1 NOTIFY=NEVER$2
+ /^(RCPT\s+TO:.*)/ $1 NOTIFY=NEVER
+</pre>
+
+<p> This feature is available in Postfix 2.7. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_data_restrictions">smtpd_data_restrictions</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional access restrictions that the Postfix SMTP server applies
+in the context of the SMTP DATA command.
+See <a href="SMTPD_ACCESS_README.html">SMTPD_ACCESS_README</a>, section "Delayed evaluation of SMTP access
+restriction lists" for a discussion of evaluation context and time.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+<p>
+Specify a list of restrictions, separated by commas and/or whitespace.
+Continue long lines by starting the next line with whitespace.
+Restrictions are applied in the order as specified; the first
+restriction that matches wins.
+</p>
+
+<p>
+The following restrictions are valid in this context:
+</p>
+
+<ul>
+
+<li><a href="#generic">Generic</a> restrictions that can be used
+in any SMTP command context, described under <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>.
+
+<li>SMTP command specific restrictions described under
+<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>, <a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>,
+<a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a> or <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>.
+
+<li>However, no recipient information is available in the case of
+multi-recipient mail. Acting on only one recipient would be misleading,
+because any decision will affect all recipients equally. Acting on
+all recipients would require a possibly very large amount of memory,
+and would also be misleading for the reasons mentioned before.
+
+</ul>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_data_restrictions">smtpd_data_restrictions</a> = <a href="postconf.5.html#reject_unauth_pipelining">reject_unauth_pipelining</a>
+<a href="postconf.5.html#smtpd_data_restrictions">smtpd_data_restrictions</a> = <a href="postconf.5.html#reject_multi_recipient_bounce">reject_multi_recipient_bounce</a>
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_delay_open_until_valid_rcpt">smtpd_delay_open_until_valid_rcpt</a>
+(default: yes)</b></DT><DD>
+
+<p> Postpone the start of an SMTP mail transaction until a valid
+RCPT TO command is received. Specify "no" to create a mail transaction
+as soon as the Postfix SMTP server receives a valid MAIL FROM
+command. </p>
+
+<p> With sites that reject lots of mail, the default setting reduces
+the use of
+disk, CPU and memory resources. The downside is that rejected
+recipients are logged with NOQUEUE instead of a mail transaction
+ID. This complicates the logfile analysis of multi-recipient mail.
+</p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_delay_reject">smtpd_delay_reject</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Wait until the RCPT TO command before evaluating
+$<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>, $<a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a> and
+$<a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a>, or wait until the ETRN command before
+evaluating $<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> and $<a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>.
+</p>
+
+<p>
+This feature is turned on by default because some clients apparently
+mis-behave when the Postfix SMTP server rejects commands before
+RCPT TO.
+</p>
+
+<p>
+The default setting has one major benefit: it allows Postfix to log
+recipient address information when rejecting a client name/address
+or sender address, so that it is possible to find out whose mail
+is being rejected.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Lookup tables, indexed by the remote SMTP client address, with
+case insensitive lists of EHLO keywords (pipelining, starttls, auth,
+etc.) that the Postfix SMTP server will not send in the EHLO response
+to a
+remote SMTP client. See <a href="postconf.5.html#smtpd_discard_ehlo_keywords">smtpd_discard_ehlo_keywords</a> for details.
+The tables are not searched by hostname for robustness reasons. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_discard_ehlo_keywords">smtpd_discard_ehlo_keywords</a>
+(default: empty)</b></DT><DD>
+
+<p> A case insensitive list of EHLO keywords (pipelining, starttls,
+auth, etc.) that the Postfix SMTP server will not send in the EHLO
+response
+to a remote SMTP client. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+<p> Notes: </p>
+
+<ul>
+
+<li> <p> Specify the <b>silent-discard</b> pseudo keyword to prevent
+this action from being logged. </p>
+
+<li> <p> Use the <a href="postconf.5.html#smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a> feature
+to discard EHLO keywords selectively. </p>
+
+</ul>
+
+
+</DD>
+
+<DT><b><a name="smtpd_dns_reply_filter">smtpd_dns_reply_filter</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional filter for Postfix SMTP server DNS lookup results.
+See <a href="postconf.5.html#smtp_dns_reply_filter">smtp_dns_reply_filter</a> for details including an example.
+</p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_end_of_data_restrictions">smtpd_end_of_data_restrictions</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional access restrictions that the Postfix SMTP server
+applies in the context of the SMTP END-OF-DATA command.
+See <a href="SMTPD_ACCESS_README.html">SMTPD_ACCESS_README</a>, section "Delayed evaluation of SMTP access
+restriction lists" for a discussion of evaluation context and time.
+</p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+<p> See <a href="postconf.5.html#smtpd_data_restrictions">smtpd_data_restrictions</a> for details and limitations. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_enforce_tls">smtpd_enforce_tls</a>
+(default: no)</b></DT><DD>
+
+<p> Mandatory TLS: announce STARTTLS support to remote SMTP clients,
+and require that clients use TLS encryption. According to <a href="http://tools.ietf.org/html/rfc2487">RFC 2487</a>
+this MUST NOT be applied in case of a publicly-referenced SMTP
+server. This option is therefore off by default. </p>
+
+<p> Note 1: "<a href="postconf.5.html#smtpd_enforce_tls">smtpd_enforce_tls</a> = yes" implies "<a href="postconf.5.html#smtpd_tls_auth_only">smtpd_tls_auth_only</a> = yes". </p>
+
+<p> Note 2: when invoked via "<b>sendmail -bs</b>", Postfix will never offer
+STARTTLS due to insufficient privileges to access the server private
+key. This is intended behavior. </p>
+
+<p> This feature is available in Postfix 2.2 and later. With
+Postfix 2.3 and later use <a href="postconf.5.html#smtpd_tls_security_level">smtpd_tls_security_level</a> instead. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_error_sleep_time">smtpd_error_sleep_time</a>
+(default: 1s)</b></DT><DD>
+
+<p>With Postfix version 2.1 and later: the SMTP server response delay after
+a client has made more than $<a href="postconf.5.html#smtpd_soft_error_limit">smtpd_soft_error_limit</a> errors, and
+fewer than $<a href="postconf.5.html#smtpd_hard_error_limit">smtpd_hard_error_limit</a> errors, without delivering mail.
+</p>
+
+<p>With Postfix version 2.0 and earlier: the SMTP server delay before
+sending a reject (4xx or 5xx) response, when the client has made
+fewer than $<a href="postconf.5.html#smtpd_soft_error_limit">smtpd_soft_error_limit</a> errors without delivering
+mail. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_etrn_restrictions">smtpd_etrn_restrictions</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional restrictions that the Postfix SMTP server applies in the
+context of a client ETRN command.
+See <a href="SMTPD_ACCESS_README.html">SMTPD_ACCESS_README</a>, section "Delayed evaluation of SMTP access
+restriction lists" for a discussion of evaluation context and time.
+</p>
+
+<p>
+The Postfix ETRN implementation accepts only destinations that are
+eligible for the Postfix "fast flush" service. See the <a href="ETRN_README.html">ETRN_README</a>
+file for details.
+</p>
+
+<p>
+Specify a list of restrictions, separated by commas and/or whitespace.
+Continue long lines by starting the next line with whitespace.
+Restrictions are applied in the order as specified; the first
+restriction that matches wins.
+</p>
+
+<p>
+The following restrictions are specific to the domain name information
+received with the ETRN command.
+</p>
+
+<dl>
+
+<dt><b><a name="check_etrn_access">check_etrn_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified access database for the ETRN domain name
+or its parent domains. See the <a href="access.5.html">access(5)</a> manual page for details.
+</dd>
+
+</dl>
+
+<p>
+Other restrictions that are valid in this context:
+</p>
+
+<ul>
+
+<li><a href="#generic">Generic</a> restrictions that can be used
+in any SMTP command context, described under <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>.
+
+<li>SMTP command specific restrictions described under
+<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> and <a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>.
+
+</ul>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_etrn_restrictions">smtpd_etrn_restrictions</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, reject
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_expansion_filter">smtpd_expansion_filter</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+What characters are allowed in $name expansions of RBL reply
+templates. Characters not in the allowed set are replaced by "_".
+Use C like escapes to specify special characters such as whitespace.
+</p>
+
+<p>
+The <a href="postconf.5.html#smtpd_expansion_filter">smtpd_expansion_filter</a> value is not subject to Postfix configuration
+parameter $name expansion.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_forbidden_commands">smtpd_forbidden_commands</a>
+(default: CONNECT, GET, POST)</b></DT><DD>
+
+<p>
+List of commands that cause the Postfix SMTP server to immediately
+terminate the session with a 221 code. This can be used to disconnect
+clients that obviously attempt to abuse the system. In addition to the
+commands listed in this parameter, commands that follow the "Label:"
+format of message headers will also cause a disconnect.
+</p>
+
+<p>
+This feature is available in Postfix 2.2 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_hard_error_limit">smtpd_hard_error_limit</a>
+(default: normal: 20, overload: 1)</b></DT><DD>
+
+<p>
+The maximal number of errors a remote SMTP client is allowed to
+make without delivering mail. The Postfix SMTP server disconnects
+when the limit is exceeded. Normally the default limit is 20, but
+it changes under overload to just 1. With Postfix 2.5 and earlier,
+the SMTP server always allows up to 20 errors by default.
+
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_helo_required">smtpd_helo_required</a>
+(default: no)</b></DT><DD>
+
+<p>
+Require that a remote SMTP client introduces itself with the HELO
+or EHLO command before sending the MAIL command or other commands
+that require EHLO negotiation.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_helo_restrictions">smtpd_helo_restrictions</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional restrictions that the Postfix SMTP server applies in the
+context of a client HELO command.
+See <a href="SMTPD_ACCESS_README.html">SMTPD_ACCESS_README</a>, section "Delayed evaluation of SMTP access
+restriction lists" for a discussion of evaluation context and time.
+</p>
+
+<p>
+The default is to permit everything.
+</p>
+
+<p> Note: specify "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes" to fully enforce this
+restriction (without "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes", a client can
+simply skip <a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a> by not sending HELO or EHLO).
+</p>
+
+<p>
+Specify a list of restrictions, separated by commas and/or whitespace.
+Continue long lines by starting the next line with whitespace.
+Restrictions are applied in the order as specified; the first
+restriction that matches wins.
+</p>
+
+<p>
+The following restrictions are specific to the hostname information
+received with the HELO or EHLO command.
+</p>
+
+<dl>
+
+<dt><b><a name="check_helo_access">check_helo_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the HELO or EHLO
+hostname or parent domains, and execute the corresponding action.
+Note: specify "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes" to fully enforce this
+restriction (without "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes", a client can
+simply skip <a href="postconf.5.html#check_helo_access">check_helo_access</a> by not sending HELO or EHLO). </dd>
+
+<dt><b><a name="check_helo_a_access">check_helo_a_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the IP addresses for
+the HELO or EHLO hostname, and execute the corresponding action.
+Note 1: a result of "OK" is not allowed for safety reasons. Instead,
+use DUNNO in order to exclude specific hosts from blacklists. Note
+2: specify "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes" to fully enforce this
+restriction (without "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes", a client can
+simply skip check_helo_a_access by not sending HELO or EHLO). This
+feature is available in Postfix 3.0 and later.
+</dd>
+
+<dt><b><a name="check_helo_mx_access">check_helo_mx_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the MX hosts for
+the HELO or EHLO hostname, and execute the corresponding action.
+Note 1: a result of "OK" is not allowed for safety reasons. Instead,
+use DUNNO in order to exclude specific hosts from blacklists. Note
+2: specify "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes" to fully enforce this
+restriction (without "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes", a client can
+simply skip <a href="postconf.5.html#check_helo_mx_access">check_helo_mx_access</a> by not sending HELO or EHLO). This
+feature is available in Postfix 2.1 and later.
+</dd>
+
+<dt><b><a name="check_helo_ns_access">check_helo_ns_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the DNS servers
+for the HELO or EHLO hostname, and execute the corresponding action.
+Note 1: a result of "OK" is not allowed for safety reasons. Instead,
+use DUNNO in order to exclude specific hosts from blacklists. Note
+2: specify "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes" to fully enforce this
+restriction (without "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes", a client can
+simply skip <a href="postconf.5.html#check_helo_ns_access">check_helo_ns_access</a> by not sending HELO or EHLO). This
+feature is available in Postfix 2.1 and later.
+</dd>
+
+<dt><b><a name="reject_invalid_helo_hostname">reject_invalid_helo_hostname</a></b> (with Postfix &lt; 2.3: reject_invalid_hostname)</dt>
+
+<dd>Reject the request when the HELO or EHLO hostname is malformed.
+Note: specify "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes" to fully enforce
+this restriction (without "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes", a client can simply
+skip <a href="postconf.5.html#reject_invalid_helo_hostname">reject_invalid_helo_hostname</a> by not sending HELO or EHLO).
+<br> The <a href="postconf.5.html#invalid_hostname_reject_code">invalid_hostname_reject_code</a> specifies the response code
+for rejected requests (default: 501).</dd>
+
+<dt><b><a name="reject_non_fqdn_helo_hostname">reject_non_fqdn_helo_hostname</a></b> (with Postfix &lt; 2.3: reject_non_fqdn_hostname)</dt>
+
+<dd>Reject the request when the HELO or EHLO hostname is not in
+fully-qualified domain or address literal form, as required by the
+RFC. Note: specify
+"<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes" to fully enforce this restriction
+(without "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes", a client can simply skip
+<a href="postconf.5.html#reject_non_fqdn_helo_hostname">reject_non_fqdn_helo_hostname</a> by not sending HELO or EHLO). <br>
+The <a href="postconf.5.html#non_fqdn_reject_code">non_fqdn_reject_code</a> parameter specifies the response code for
+rejected requests (default: 504).</dd>
+
+<dt><b><a name="reject_rhsbl_helo">reject_rhsbl_helo <i>rbl_domain=d.d.d.d</i></a></b></dt>
+
+<dd>Reject the request when the HELO or EHLO hostname is
+listed with the A record "<i>d.d.d.d</i>" under <i>rbl_domain</i>
+(Postfix version 2.1 and later only). Each "<i>d</i>" is a number,
+or a pattern inside "[]" that contains one or more ";"-separated
+numbers or number..number ranges (Postfix version 2.8 and later).
+If no "<i>=d.d.d.d</i>" is
+specified, reject the request when the HELO or EHLO hostname is
+listed with any A record under <i>rbl_domain</i>. See the
+<a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a> description for additional RBL related configuration
+parameters. Note: specify "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes" to fully
+enforce this restriction (without "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes", a
+client can simply skip <a href="postconf.5.html#reject_rhsbl_helo">reject_rhsbl_helo</a> by not sending HELO or
+EHLO). This feature is available in Postfix 2.0
+and later. </dd>
+
+<dt><b><a name="reject_unknown_helo_hostname">reject_unknown_helo_hostname</a></b> (with Postfix &lt; 2.3: reject_unknown_hostname)</dt>
+
+<dd>Reject the request when the HELO or EHLO hostname has no DNS A
+or MX record. <br> The reply is specified with the
+<a href="postconf.5.html#unknown_hostname_reject_code">unknown_hostname_reject_code</a> parameter (default: 450) or
+<a href="postconf.5.html#unknown_helo_hostname_tempfail_action">unknown_helo_hostname_tempfail_action</a> (default: <a href="postconf.5.html#defer_if_permit">defer_if_permit</a>).
+See the respective parameter descriptions for details. <br>
+Note: specify "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes" to fully
+enforce this restriction (without "<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes", a
+client can simply skip <a href="postconf.5.html#reject_unknown_helo_hostname">reject_unknown_helo_hostname</a> by not sending
+HELO or EHLO). </dd>
+
+</dl>
+
+<p>
+Other restrictions that are valid in this context:
+</p>
+
+<ul>
+
+<li> <a href="#generic">Generic</a> restrictions that can be used
+in any SMTP command context, described under <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>.
+
+<li> Client hostname or network address specific restrictions
+described under <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>.
+
+<li> SMTP command specific restrictions described under
+<a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a> or <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>. When
+sender or recipient restrictions are listed under <a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>,
+they have effect only with "<a href="postconf.5.html#smtpd_delay_reject">smtpd_delay_reject</a> = yes", so that
+$<a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a> is evaluated at the time of the RCPT TO
+command.
+
+</ul>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, <a href="postconf.5.html#reject_invalid_helo_hostname">reject_invalid_helo_hostname</a>
+<a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, <a href="postconf.5.html#reject_unknown_helo_hostname">reject_unknown_helo_hostname</a>
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_history_flush_threshold">smtpd_history_flush_threshold</a>
+(default: 100)</b></DT><DD>
+
+<p>
+The maximal number of lines in the Postfix SMTP server command history
+before it is flushed upon receipt of EHLO, RSET, or end of DATA.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_junk_command_limit">smtpd_junk_command_limit</a>
+(default: normal: 100, overload: 1)</b></DT><DD>
+
+<p>
+The number of junk commands (NOOP, VRFY, ETRN or RSET) that a remote
+SMTP client can send before the Postfix SMTP server starts to
+increment the error counter with each junk command. The junk
+command count is reset after mail is delivered. See also the
+<a href="postconf.5.html#smtpd_error_sleep_time">smtpd_error_sleep_time</a> and <a href="postconf.5.html#smtpd_soft_error_limit">smtpd_soft_error_limit</a> configuration
+parameters. Normally the default limit is 100, but it changes under
+overload to just 1. With Postfix 2.5 and earlier, the SMTP server
+always allows up to 100 junk commands by default. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_log_access_permit_actions">smtpd_log_access_permit_actions</a>
+(default: empty)</b></DT><DD>
+
+<p> Enable logging of the named "permit" actions in SMTP server
+access lists (by default, the SMTP server logs "reject" actions but
+not "permit" actions). This feature does not affect conditional
+actions such as "<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>". </p>
+
+<p> Specify a list of "permit" action names, "/file/name" or
+"<a href="DATABASE_README.html">type:table</a>" patterns, separated by commas and/or whitespace. The
+list is matched left to right, and the search stops on the first
+match. A "/file/name" pattern is replaced by its contents; a
+"<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name matches a lookup
+key (the lookup result is ignored). Continue long lines by starting
+the next line with whitespace. Specify "!pattern" to exclude a name
+from the list. </p>
+
+<p> Examples: </p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ # Log all "permit" actions.
+ <a href="postconf.5.html#smtpd_log_access_permit_actions">smtpd_log_access_permit_actions</a> = <a href="DATABASE_README.html#types">static</a>:all
+</pre>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ # Log "<a href="postconf.5.html#permit_dnswl_client">permit_dnswl_client</a>" only.
+ <a href="postconf.5.html#smtpd_log_access_permit_actions">smtpd_log_access_permit_actions</a> = <a href="postconf.5.html#permit_dnswl_client">permit_dnswl_client</a>
+</pre>
+
+<p> This feature is available in Postfix 2.10 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_milter_maps">smtpd_milter_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Lookup tables with Milter settings per remote SMTP client IP
+address. The lookup result overrides the <a href="postconf.5.html#smtpd_milters">smtpd_milters</a> setting,
+and has the same syntax. </p>
+
+<p> Note: lookup tables cannot return empty responses. Specify a
+lookup result of DISABLE (case does not matter) to indicate that
+Milter support should be disabled. </p>
+
+<p> Example to disable Milters for local clients: </p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtpd_milter_maps">smtpd_milter_maps</a> = <a href="cidr_table.5.html">cidr</a>:/etc/postfix/smtpd_milter_map
+ <a href="postconf.5.html#smtpd_milters">smtpd_milters</a> = inet:host:port, { inet:host:port, ... }, ...
+</pre>
+
+<pre>
+/etc/postfix/smtpd_milter_map:
+ # Disable Milters for local clients.
+ 127.0.0.0/8 DISABLE
+ 192.168.0.0/16 DISABLE
+ ::/64 DISABLE
+ 2001:db8::/32 DISABLE
+</pre>
+
+<p> This feature is available in Postfix 3.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_milters">smtpd_milters</a>
+(default: empty)</b></DT><DD>
+
+<p> A list of Milter (mail filter) applications for new mail that
+arrives via the Postfix <a href="smtpd.8.html">smtpd(8)</a> server. Specify space or comma as
+separator. See the <a href="MILTER_README.html">MILTER_README</a> document for details. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_noop_commands">smtpd_noop_commands</a>
+(default: empty)</b></DT><DD>
+
+<p>
+List of commands that the Postfix SMTP server replies to with "250
+Ok", without doing any syntax checks and without changing state.
+This list overrides any commands built into the Postfix SMTP server.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_null_access_lookup_key">smtpd_null_access_lookup_key</a>
+(default: &lt;&gt;)</b></DT><DD>
+
+<p>
+The lookup key to be used in SMTP <a href="access.5.html">access(5)</a> tables instead of the
+null sender address.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_peername_lookup">smtpd_peername_lookup</a>
+(default: yes)</b></DT><DD>
+
+<p> Attempt to look up the remote SMTP client hostname, and verify that
+the name matches the client IP address. A client name is set to
+"unknown" when it cannot be looked up or verified, or when name
+lookup is disabled. Turning off name lookup reduces delays due to
+DNS lookup and increases the maximal inbound delivery rate. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_per_record_deadline">smtpd_per_record_deadline</a>
+(default: normal: no, overload: yes)</b></DT><DD>
+
+<p> Change the behavior of the <a href="postconf.5.html#smtpd_timeout">smtpd_timeout</a> and <a href="postconf.5.html#smtpd_starttls_timeout">smtpd_starttls_timeout</a>
+time limits, from a
+time limit per read or write system call, to a time limit to send
+or receive a complete record (an SMTP command line, SMTP response
+line, SMTP message content line, or TLS protocol message). This
+limits the impact from hostile peers that trickle data one byte at
+a time. </p>
+
+<p> Note: when per-record deadlines are enabled, a short timeout
+may cause problems with TLS over very slow network connections.
+The reasons are that a TLS protocol message can be up to 16 kbytes
+long (with TLSv1), and that an entire TLS protocol message must be
+sent or received within the per-record deadline. </p>
+
+<p> This feature is available in Postfix 2.9 and later. With older
+Postfix releases, the behavior is as if this parameter is set to
+"no". </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_policy_service_default_action">smtpd_policy_service_default_action</a>
+(default: 451 4.3.5 Server configuration problem)</b></DT><DD>
+
+<p> The default action when an SMTPD policy service request fails.
+Specify "DUNNO" to behave as if the failed SMTPD policy service
+request was not sent, and to continue processing other access
+restrictions, if any. </p>
+
+<p> Limitations: </p>
+
+<ul>
+
+<li> <p> This parameter may specify any value that would be a valid
+SMTPD policy server response (or <a href="access.5.html">access(5)</a> map lookup result). An
+<a href="access.5.html">access(5)</a> map or policy server in this parameter value may need to
+be declared in advance with a restriction_class setting. </p>
+
+<li> <p> If the specified action invokes another <a href="postconf.5.html#check_policy_service">check_policy_service</a>
+request, that request will have the built-in default action. </p>
+
+</ul>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_policy_service_max_idle">smtpd_policy_service_max_idle</a>
+(default: 300s)</b></DT><DD>
+
+<p>
+The time after which an idle SMTPD policy service connection is
+closed.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_policy_service_max_ttl">smtpd_policy_service_max_ttl</a>
+(default: 1000s)</b></DT><DD>
+
+<p>
+The time after which an active SMTPD policy service connection is
+closed.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_policy_service_policy_context">smtpd_policy_service_policy_context</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional information that the Postfix SMTP server specifies in
+the "policy_context" attribute of a policy service request (originally,
+to share the same service endpoint among multiple <a href="postconf.5.html#check_policy_service">check_policy_service</a>
+clients). </p>
+
+<p>
+This feature is available in Postfix 3.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_policy_service_request_limit">smtpd_policy_service_request_limit</a>
+(default: 0)</b></DT><DD>
+
+<p>
+The maximal number of requests per SMTPD policy service connection,
+or zero (no limit). Once a connection reaches this limit, the
+connection is closed and the next request will be sent over a new
+connection. This is a workaround to avoid error-recovery delays
+with policy servers that cannot maintain a persistent connection.
+</p>
+
+<p>
+This feature is available in Postfix 3.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_policy_service_retry_delay">smtpd_policy_service_retry_delay</a>
+(default: 1s)</b></DT><DD>
+
+<p> The delay between attempts to resend a failed SMTPD policy
+service request. Specify a value greater than zero. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_policy_service_timeout">smtpd_policy_service_timeout</a>
+(default: 100s)</b></DT><DD>
+
+<p>
+The time limit for connecting to, writing to, or receiving from a
+delegated SMTPD policy server.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_policy_service_try_limit">smtpd_policy_service_try_limit</a>
+(default: 2)</b></DT><DD>
+
+<p> The maximal number of attempts to send an SMTPD policy service
+request before giving up. Specify a value greater than zero. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_proxy_ehlo">smtpd_proxy_ehlo</a>
+(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</b></DT><DD>
+
+<p>
+How the Postfix SMTP server announces itself to the proxy filter.
+By default, the Postfix hostname is used.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_proxy_filter">smtpd_proxy_filter</a>
+(default: empty)</b></DT><DD>
+
+<p> The hostname and TCP port of the mail filtering proxy server.
+The proxy receives all mail from the Postfix SMTP server, and is
+supposed to give the result to another Postfix SMTP server process.
+</p>
+
+<p> Specify "host:port" or "inet:host:port" for a TCP endpoint, or
+"unix:pathname" for a UNIX-domain endpoint. The host can be specified
+as an IP address or as a symbolic name; no MX lookups are done.
+When no "host" or "host:" are specified, the local machine is
+assumed. Pathname interpretation is relative to the Postfix queue
+directory. </p>
+
+<p> This feature is available in Postfix 2.1 and later. </p>
+
+<p> The "inet:" and "unix:" prefixes are available in Postfix 2.3
+and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_proxy_options">smtpd_proxy_options</a>
+(default: empty)</b></DT><DD>
+
+<p>
+List of options that control how the Postfix SMTP server
+communicates with a before-queue content filter. Specify zero or
+more of the following, separated by comma or whitespace. </p>
+
+<dl>
+
+<dt><b>speed_adjust</b></dt>
+
+<dd> <p> Do not connect to a before-queue content filter until an entire
+message has been received. This reduces the number of simultaneous
+before-queue content filter processes. </p>
+
+<p> NOTE 1: A filter must not <i>selectively</i> reject recipients
+of a multi-recipient message. Rejecting all recipients is OK, as
+is accepting all recipients. </p>
+
+<p> NOTE 2: This feature increases the minimum amount of free queue
+space by $<a href="postconf.5.html#message_size_limit">message_size_limit</a>. The extra space is needed to save the
+message to a temporary file. </p> </dd>
+
+</dl>
+
+<p>
+This feature is available in Postfix 2.7 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_proxy_timeout">smtpd_proxy_timeout</a>
+(default: 100s)</b></DT><DD>
+
+<p>
+The time limit for connecting to a proxy filter and for sending or
+receiving information. When a connection fails the client gets a
+generic error message while more detailed information is logged to
+the maillog file.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_recipient_limit">smtpd_recipient_limit</a>
+(default: 1000)</b></DT><DD>
+
+<p>
+The maximal number of recipients that the Postfix SMTP server
+accepts per message delivery request.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_recipient_overshoot_limit">smtpd_recipient_overshoot_limit</a>
+(default: 1000)</b></DT><DD>
+
+<p> The number of recipients that a remote SMTP client can send in
+excess of the limit specified with $<a href="postconf.5.html#smtpd_recipient_limit">smtpd_recipient_limit</a>, before
+the Postfix SMTP server increments the per-session error count
+for each excess recipient. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+Optional restrictions that the Postfix SMTP server applies in the
+context of a client RCPT TO command, after <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a>.
+See <a href="SMTPD_ACCESS_README.html">SMTPD_ACCESS_README</a>, section "Delayed evaluation of SMTP access
+restriction lists" for a discussion of evaluation context and time.
+</p>
+
+<p> With Postfix versions before 2.10, the rules for relay permission
+and spam blocking were combined under <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>,
+resulting in error-prone configuration. As of Postfix 2.10, relay
+permission rules are preferably implemented with <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a>,
+so that a permissive spam blocking policy under
+<a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> will no longer result in a permissive
+mail relay policy. </p>
+
+<p> For backwards compatibility, sites that migrate from Postfix
+versions before 2.10 can set <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a> to the empty
+value, and use <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> exactly as before. </p>
+
+<p>
+IMPORTANT: Either the <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a> or the
+<a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> parameter must specify
+at least one of the following restrictions. Otherwise Postfix will
+refuse to receive mail:
+</p>
+
+<blockquote>
+<pre>
+reject, <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a>
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+defer, <a href="postconf.5.html#defer_if_permit">defer_if_permit</a>, <a href="postconf.5.html#defer_unauth_destination">defer_unauth_destination</a>
+</pre>
+</blockquote>
+
+<p>
+Specify a list of restrictions, separated by commas and/or whitespace.
+Continue long lines by starting the next line with whitespace.
+Restrictions are applied in the order as specified; the first
+restriction that matches wins.
+</p>
+
+<p>
+The following restrictions are specific to the recipient address
+that is received with the RCPT TO command.
+</p>
+
+<dl>
+
+<dt><b><a name="check_recipient_access">check_recipient_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the resolved RCPT
+TO address, domain, parent domains, or localpart@, and execute the
+corresponding action. </dd>
+
+<dt><b><a name="check_recipient_a_access">check_recipient_a_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the IP addresses for
+the RCPT TO domain, and execute the corresponding action. Note:
+a result of "OK" is not allowed for safety reasons. Instead, use
+DUNNO in order to exclude specific hosts from blacklists. This
+feature is available in Postfix 3.0 and later. </dd>
+
+<dt><b><a name="check_recipient_mx_access">check_recipient_mx_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the MX hosts for
+the RCPT TO domain, and execute the corresponding action. Note:
+a result of "OK" is not allowed for safety reasons. Instead, use
+DUNNO in order to exclude specific hosts from blacklists. This
+feature is available in Postfix 2.1 and later. </dd>
+
+<dt><b><a name="check_recipient_ns_access">check_recipient_ns_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the DNS servers
+for the RCPT TO domain, and execute the corresponding action.
+Note: a result of "OK" is not allowed for safety reasons. Instead,
+use DUNNO in order to exclude specific hosts from blacklists. This
+feature is available in Postfix 2.1 and later. </dd>
+
+<dt><b><a name="permit_auth_destination">permit_auth_destination</a></b></dt>
+
+<dd>Permit the request when one of the following is true:
+
+<ul>
+
+<li> Postfix is mail forwarder: the resolved RCPT TO domain matches
+$<a href="postconf.5.html#relay_domains">relay_domains</a> or a subdomain thereof, and the address contains no
+sender-specified routing (user@elsewhere@domain),
+
+<li> Postfix is the final destination: the resolved RCPT TO domain
+matches $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>, $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>,
+$<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, or $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>, and the address
+contains no sender-specified routing (user@elsewhere@domain).
+
+</ul></dd>
+
+<dt><b><a name="permit_mx_backup">permit_mx_backup</a></b></dt>
+
+<dd>Permit the request when the local mail system is backup MX for
+the RCPT TO domain, or when the domain is an authorized destination
+(see <a href="postconf.5.html#permit_auth_destination">permit_auth_destination</a> for definition).
+
+<ul>
+
+<li> Safety: <a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> does not accept addresses that have
+sender-specified routing information (example: user@elsewhere@domain).
+
+<li> Safety: <a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> can be vulnerable to mis-use when
+access is not restricted with <a href="postconf.5.html#permit_mx_backup_networks">permit_mx_backup_networks</a>.
+
+<li> Safety: as of Postfix version 2.3, <a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> no longer
+accepts the address when the local mail system is primary MX for
+the recipient domain. Exception: <a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> accepts the address
+when it specifies an authorized destination (see <a href="postconf.5.html#permit_auth_destination">permit_auth_destination</a>
+for definition).
+
+<li> Limitation: mail may be rejected in case of a temporary DNS
+lookup problem with Postfix prior to version 2.0.
+
+</ul></dd>
+
+<dt><b><a name="reject_non_fqdn_recipient">reject_non_fqdn_recipient</a></b></dt>
+
+<dd>Reject the request when the RCPT TO address specifies a
+domain that is not in
+fully-qualified domain form, as required by the RFC. <br> The
+<a href="postconf.5.html#non_fqdn_reject_code">non_fqdn_reject_code</a> parameter specifies the response code for
+rejected requests (default: 504). </dd>
+
+<dt><b><a name="reject_rhsbl_recipient">reject_rhsbl_recipient <i>rbl_domain=d.d.d.d</i></a></b></dt>
+
+<dd>Reject the request when the RCPT TO domain is listed with the
+A record "<i>d.d.d.d</i>" under <i>rbl_domain</i> (Postfix version
+2.1 and later only). Each "<i>d</i>" is a number, or a pattern
+inside "[]" that contains one or more ";"-separated numbers or
+number..number ranges (Postfix version 2.8 and later). If no
+"<i>=d.d.d.d</i>" is specified, reject
+the request when the RCPT TO domain is listed with
+any A record under <i>rbl_domain</i>. <br> The <a href="postconf.5.html#maps_rbl_reject_code">maps_rbl_reject_code</a>
+parameter specifies the response code for rejected requests (default:
+554); the <a href="postconf.5.html#default_rbl_reply">default_rbl_reply</a> parameter specifies the default server
+reply; and the <a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a> parameter specifies tables with server
+replies indexed by <i>rbl_domain</i>. This feature is available
+in Postfix version 2.0 and later.</dd>
+
+<dt><b><a name="reject_unauth_destination">reject_unauth_destination</a></b></dt>
+
+<dd>Reject the request unless one of the following is true:
+
+<ul>
+
+<li> Postfix is mail forwarder: the resolved RCPT TO domain matches
+$<a href="postconf.5.html#relay_domains">relay_domains</a> or a subdomain thereof, and contains no sender-specified
+routing (user@elsewhere@domain),
+
+<li> Postfix is the final destination: the resolved RCPT TO domain
+matches $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>, $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>,
+$<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, or $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>, and contains
+no sender-specified routing (user@elsewhere@domain).
+
+</ul>The <a href="postconf.5.html#relay_domains_reject_code">relay_domains_reject_code</a> parameter specifies the response
+code for rejected requests (default: 554). </dd>
+
+<dt><b><a name="defer_unauth_destination">defer_unauth_destination</a></b></dt>
+
+<dd> Reject the same requests as <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a>, with a
+non-permanent error code. This feature is available in Postfix
+2.10 and later.</dd>
+
+<dt><b><a name="reject_unknown_recipient_domain">reject_unknown_recipient_domain</a></b></dt>
+
+<dd>Reject the request when Postfix is not final destination for
+the recipient domain, and the RCPT TO domain has 1) no DNS MX and
+no DNS A
+record or 2) a malformed MX record such as a record with
+a zero-length MX hostname (Postfix version 2.3 and later). <br> The
+reply is specified with the <a href="postconf.5.html#unknown_address_reject_code">unknown_address_reject_code</a> parameter
+(default: 450), <a href="postconf.5.html#unknown_address_tempfail_action">unknown_address_tempfail_action</a> (default:
+<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>), or 556 (nullmx, Postfix 3.0 and
+later). See the respective parameter descriptions for details.
+</dd>
+
+<dt><b><a name="reject_unlisted_recipient">reject_unlisted_recipient</a></b> (with Postfix version 2.0: check_recipient_maps)</dt>
+
+<dd> Reject the request when the RCPT TO address is not listed in
+the list of valid recipients for its domain class. See the
+<a href="postconf.5.html#smtpd_reject_unlisted_recipient">smtpd_reject_unlisted_recipient</a> parameter description for details.
+This feature is available in Postfix 2.1 and later.</dd>
+
+<dt><b><a name="reject_unverified_recipient">reject_unverified_recipient</a></b></dt>
+
+<dd>Reject the request when mail to the RCPT TO address is known
+to bounce, or when the recipient address destination is not reachable.
+Address verification information is managed by the <a href="verify.8.html">verify(8)</a> server;
+see the <a href="ADDRESS_VERIFICATION_README.html">ADDRESS_VERIFICATION_README</a> file for details. <br> The
+<a href="postconf.5.html#unverified_recipient_reject_code">unverified_recipient_reject_code</a> parameter specifies the numerical
+response code when an address is known to bounce (default: 450,
+change into 550 when you are confident that it is safe to do so).
+<br>The <a href="postconf.5.html#unverified_recipient_defer_code">unverified_recipient_defer_code</a> parameter specifies the
+numerical response code when an address probe failed due to a
+temporary problem (default: 450). <br> The
+<a href="postconf.5.html#unverified_recipient_tempfail_action">unverified_recipient_tempfail_action</a> parameter specifies the action
+after address probe failure due to a temporary problem (default:
+<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>). <br> This feature breaks for aliased addresses
+with "<a href="postconf.5.html#enable_original_recipient">enable_original_recipient</a> = no" (Postfix &le; 3.2). <br>
+This feature is available in Postfix 2.1 and later. </dd>
+
+</dl>
+
+<p>
+Other restrictions that are valid in this context:
+</p>
+
+<ul>
+
+<li><a href="#generic">Generic</a> restrictions that can be used
+in any SMTP command context, described under <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>.
+
+<li>SMTP command specific restrictions described under
+<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>, <a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a> and
+<a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a>.
+
+</ul>
+
+<p>
+Example:
+</p>
+
+<pre>
+# The Postfix before 2.10 default mail relay policy. Later Postfix
+# versions implement this preferably with <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a>.
+<a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a>
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_reject_footer">smtpd_reject_footer</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional information that is appended after each Postfix SMTP
+server
+4XX or 5XX response. </p>
+
+<p> The following example uses "\c" at the start of the template
+(supported in Postfix 2.10 and later) to suppress the line break
+between the reply text and the footer text. With earlier Postfix
+versions, the footer text always begins on a new line, and the "\c"
+is output literally. </p>
+
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtpd_reject_footer">smtpd_reject_footer</a> = \c. For assistance, call 800-555-0101.
+ Please provide the following information in your problem report:
+ time ($localtime), client ($client_address) and server
+ ($server_name).
+</pre>
+
+<p> Server response: </p>
+
+<pre>
+ 550-5.5.1 &lt;user@example&gt; Recipient address rejected: User
+ unknown. For assistance, call 800-555-0101. Please provide the
+ following information in your problem report: time (Jan 4 15:42:00),
+ client (192.168.1.248) and server (mail1.example.com).
+</pre>
+
+<p> Note: the above text is meant to make it easier to find the
+Postfix logfile records for a failed SMTP session. The text itself
+is not logged to the Postfix SMTP server's maillog file. </p>
+
+<p> Be sure to keep the text as short as possible. Long text may
+be truncated before it is logged to the remote SMTP client's maillog
+file, or before it is returned to the sender in a delivery status
+notification. </p>
+
+<p> The template text is not subject to Postfix configuration
+parameter $name expansion. Instead, this feature supports a limited
+number of $name attributes in the footer text. These attributes are
+replaced with their current value for the SMTP session. </p>
+
+<p> Note: specify $$name in footer text that is looked up from
+<a href="regexp_table.5.html">regexp</a>: or <a href="pcre_table.5.html">pcre</a>:-based <a href="postconf.5.html#smtpd_reject_footer_maps">smtpd_reject_footer_maps</a>, otherwise the
+Postfix server will not use the footer text and will log a warning
+instead. </p>
+
+<dl>
+
+<dt> <b>client_address</b> </dt> <dd> The Client IP address that
+is logged in the maillog file. </dd>
+
+<dt> <b>client_port</b> </dt> <dd> The client TCP port that is
+logged in the maillog file. </dd>
+
+<dt> <b>localtime</b> </dt> <dd> The server local time (Mmm dd
+hh:mm:ss) that is logged in the maillog file. </dd>
+
+<dt> <b>server_name</b> </dt> <dd> The server's <a href="postconf.5.html#myhostname">myhostname</a> value.
+This attribute is made available for sites with multiple MTAs
+(perhaps behind a load-balancer), where the server name can help
+the server support team to quickly find the right log files. </dd>
+
+</dl>
+
+<p> Notes: </p>
+
+<ul>
+
+<li> <p> NOT SUPPORTED are other attributes such as sender, recipient,
+or <a href="postconf.5.html">main.cf</a> parameters. </p>
+
+<li> <p> For safety reasons, text that does not match
+$<a href="postconf.5.html#smtpd_expansion_filter">smtpd_expansion_filter</a> is censored. </p>
+
+</ul>
+
+<p> This feature supports the two-character sequence \n as a request
+for a line break in the footer text. Postfix automatically inserts
+after each line break the three-digit SMTP reply code (and optional
+enhanced status code) from the original Postfix reject message.
+</p>
+
+<p> To work around mail software that mis-handles multi-line replies,
+specify the two-character sequence \c at the start of the template.
+This suppresses the line break between the reply text and the footer
+text (Postfix 2.10 and later). </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_reject_footer_maps">smtpd_reject_footer_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Lookup tables, indexed by the complete Postfix SMTP server 4xx or
+5xx response, with reject footer templates. See <a href="postconf.5.html#smtpd_reject_footer">smtpd_reject_footer</a>
+for details. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_reject_unlisted_recipient">smtpd_reject_unlisted_recipient</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Request that the Postfix SMTP server rejects mail for unknown
+recipient addresses, even when no explicit <a href="postconf.5.html#reject_unlisted_recipient">reject_unlisted_recipient</a>
+access restriction is specified. This prevents the Postfix queue
+from filling up with undeliverable MAILER-DAEMON messages.
+</p>
+
+<p> An address is always considered "known" when it matches a
+<a href="virtual.5.html">virtual(5)</a> alias or a <a href="canonical.5.html">canonical(5)</a> mapping.
+
+<ul>
+
+<li> The recipient domain matches $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
+or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>, but the recipient is not listed in
+$<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a>, and $<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> is not null.
+
+<li> The recipient domain matches $<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a> but the
+recipient is not listed in $<a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a>.
+
+<li> The recipient domain matches $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a> but the
+recipient is not listed in $<a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a>, and $<a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a>
+is not null.
+
+<li> The recipient domain matches $<a href="postconf.5.html#relay_domains">relay_domains</a> but the recipient
+is not listed in $<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a>, and $<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a>
+is not null.
+
+</ul>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_reject_unlisted_sender">smtpd_reject_unlisted_sender</a>
+(default: no)</b></DT><DD>
+
+<p> Request that the Postfix SMTP server rejects mail from unknown
+sender addresses, even when no explicit <a href="postconf.5.html#reject_unlisted_sender">reject_unlisted_sender</a>
+access restriction is specified. This can slow down an explosion
+of forged mail from worms or viruses. </p>
+
+<p> An address is always considered "known" when it matches a
+<a href="virtual.5.html">virtual(5)</a> alias or a <a href="canonical.5.html">canonical(5)</a> mapping.
+
+<ul>
+
+<li> The sender domain matches $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or
+$<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>, but the sender is not listed in
+$<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a>, and $<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> is not null.
+
+<li> The sender domain matches $<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a> but the sender
+is not listed in $<a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a>.
+
+<li> The sender domain matches $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a> but the
+sender is not listed in $<a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a>, and $<a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a>
+is not null.
+
+<li> The sender domain matches $<a href="postconf.5.html#relay_domains">relay_domains</a> but the sender is
+not listed in $<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a>, and $<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> is
+not null.
+
+</ul>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_relay_restrictions">smtpd_relay_restrictions</a>
+(default: <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, <a href="postconf.5.html#permit_sasl_authenticated">permit_sasl_authenticated</a>, <a href="postconf.5.html#defer_unauth_destination">defer_unauth_destination</a>)</b></DT><DD>
+
+<p> Access restrictions for mail relay control that the Postfix
+SMTP server applies in the context of the RCPT TO command, before
+<a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>.
+See <a href="SMTPD_ACCESS_README.html">SMTPD_ACCESS_README</a>, section "Delayed evaluation of SMTP access
+restriction lists" for a discussion of evaluation context and time.
+</p>
+
+<p> With Postfix versions before 2.10, the rules for relay permission
+and spam blocking were combined under <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>,
+resulting in error-prone configuration. As of Postfix 2.10, relay
+permission rules are preferably implemented with <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a>,
+so that a permissive spam blocking policy under
+<a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> will no longer result in a permissive
+mail relay policy. </p>
+
+<p> For backwards compatibility, sites that migrate from Postfix
+versions before 2.10 can set <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a> to the empty
+value, and use <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> exactly as before. </p>
+
+<p>
+By default, the Postfix SMTP server accepts:
+</p>
+
+<ul>
+
+<li> Mail from clients whose IP address matches $<a href="postconf.5.html#mynetworks">mynetworks</a>, or:
+
+<li> Mail to remote destinations that match $<a href="postconf.5.html#relay_domains">relay_domains</a>, except
+for addresses that contain sender-specified routing
+(user@elsewhere@domain), or:
+
+<li> Mail to local destinations that match $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
+or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, or
+$<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>.
+
+</ul>
+
+<p>
+IMPORTANT: Either the <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a> or the
+<a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> parameter must specify
+at least one of the following restrictions. Otherwise Postfix will
+refuse to receive mail:
+</p>
+
+<blockquote>
+<pre>
+reject, <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a>
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+defer, <a href="postconf.5.html#defer_if_permit">defer_if_permit</a>, <a href="postconf.5.html#defer_unauth_destination">defer_unauth_destination</a>
+</pre>
+</blockquote>
+
+<p>
+Specify a list of restrictions, separated by commas and/or whitespace.
+Continue long lines by starting the next line with whitespace.
+The same restrictions are available as documented under
+<a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>.
+</p>
+
+<p> This feature is available in Postix 2.10 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_restriction_classes">smtpd_restriction_classes</a>
+(default: empty)</b></DT><DD>
+
+<p>
+User-defined aliases for groups of access restrictions. The aliases
+can be specified in <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> etc., and on the
+right-hand side of a Postfix <a href="access.5.html">access(5)</a> table.
+</p>
+
+<p>
+One major application is for implementing per-recipient UCE control.
+See the <a href="RESTRICTION_CLASS_README.html">RESTRICTION_CLASS_README</a> document for other examples.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sasl_application_name">smtpd_sasl_application_name</a>
+(default: smtpd)</b></DT><DD>
+
+<p>
+The application name that the Postfix SMTP server uses for SASL
+server initialization. This
+controls the name of the SASL configuration file. The default value
+is <b>smtpd</b>, corresponding to a SASL configuration file named
+<b>smtpd.conf</b>.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and 2.2. With Postfix 2.3
+it was renamed to <a href="postconf.5.html#smtpd_sasl_path">smtpd_sasl_path</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sasl_auth_enable">smtpd_sasl_auth_enable</a>
+(default: no)</b></DT><DD>
+
+<p>
+Enable SASL authentication in the Postfix SMTP server. By default,
+the Postfix SMTP server does not use authentication.
+</p>
+
+<p>
+If a remote SMTP client is authenticated, the <a href="postconf.5.html#permit_sasl_authenticated">permit_sasl_authenticated</a>
+access restriction can be used to permit relay access, like this:
+</p>
+
+<blockquote>
+<pre>
+# With Postfix 2.10 and later, the mail relay policy is
+# preferably specified under <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a>.
+<a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a> =
+ <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, <a href="postconf.5.html#permit_sasl_authenticated">permit_sasl_authenticated</a>, ...
+</pre>
+
+<pre>
+# With Postfix before 2.10, the relay policy can be
+# specified only under <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>.
+<a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> =
+ <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, <a href="postconf.5.html#permit_sasl_authenticated">permit_sasl_authenticated</a>, ...
+</pre>
+</blockquote>
+
+<p> To reject all SMTP connections from unauthenticated clients,
+specify "<a href="postconf.5.html#smtpd_delay_reject">smtpd_delay_reject</a> = yes" (which is the default) and use:
+</p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> = <a href="postconf.5.html#permit_sasl_authenticated">permit_sasl_authenticated</a>, reject
+</pre>
+</blockquote>
+
+<p>
+See the <a href="SASL_README.html">SASL_README</a> file for SASL configuration and operation details.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sasl_authenticated_header">smtpd_sasl_authenticated_header</a>
+(default: no)</b></DT><DD>
+
+<p> Report the SASL authenticated user name in the <a href="smtpd.8.html">smtpd(8)</a> Received
+message header. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sasl_exceptions_networks">smtpd_sasl_exceptions_networks</a>
+(default: empty)</b></DT><DD>
+
+<p>
+What remote SMTP clients the Postfix SMTP server will not offer
+AUTH support to.
+</p>
+
+<p>
+Some clients (Netscape 4 at least) have a bug that causes them to
+require a login and password whenever AUTH is offered, whether it's
+necessary or not. To work around this, specify, for example,
+$<a href="postconf.5.html#mynetworks">mynetworks</a> to prevent Postfix from offering AUTH to local clients.
+</p>
+
+<p>
+Specify a list of network/netmask patterns, separated by commas
+and/or whitespace. The mask specifies the number of bits in the
+network part of a host address. You can also "/file/name" or
+"<a href="DATABASE_README.html">type:table</a>" patterns. A "/file/name" pattern is replaced by its
+contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a table entry
+matches a lookup string (the lookup result is ignored). Continue
+long lines by starting the next line with whitespace. Specify
+"!pattern" to exclude an address or network block from the list.
+The form "!/file/name" is supported only in Postfix version 2.4 and
+later. </p>
+
+<p> Note: IP version 6 address information must be specified inside
+<tt>[]</tt> in the <a href="postconf.5.html#smtpd_sasl_exceptions_networks">smtpd_sasl_exceptions_networks</a> value, and in
+files specified with "/file/name". IP version 6 addresses contain
+the ":" character, and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>"
+pattern. </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_sasl_exceptions_networks">smtpd_sasl_exceptions_networks</a> = $<a href="postconf.5.html#mynetworks">mynetworks</a>
+</pre>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sasl_local_domain">smtpd_sasl_local_domain</a>
+(default: empty)</b></DT><DD>
+
+<p>
+The name of the Postfix SMTP server's local SASL authentication
+realm.
+</p>
+
+<p>
+By default, the local authentication realm name is the null string.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_sasl_local_domain">smtpd_sasl_local_domain</a> = $<a href="postconf.5.html#mydomain">mydomain</a>
+<a href="postconf.5.html#smtpd_sasl_local_domain">smtpd_sasl_local_domain</a> = $<a href="postconf.5.html#myhostname">myhostname</a>
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sasl_path">smtpd_sasl_path</a>
+(default: smtpd)</b></DT><DD>
+
+<p> Implementation-specific information that the Postfix SMTP server
+passes through to
+the SASL plug-in implementation that is selected with
+<b><a href="postconf.5.html#smtpd_sasl_type">smtpd_sasl_type</a></b>. Typically this specifies the name of a
+configuration file or rendezvous point. </p>
+
+<p> This feature is available in Postfix 2.3 and later. In earlier
+releases it was called <b><a href="postconf.5.html#smtpd_sasl_application_name">smtpd_sasl_application_name</a></b>. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sasl_response_limit">smtpd_sasl_response_limit</a>
+(default: 12288)</b></DT><DD>
+
+<p> The maximum length of a SASL client's response to a server challenge.
+When the client's "initial response" is longer than the normal limit for
+SMTP commands, the client must omit its initial response, and wait for an
+empty server challenge; it can then send what would have been its "initial
+response" as a response to the empty server challenge. <a href="http://tools.ietf.org/html/rfc4954">RFC4954</a> requires the
+server to accept client responses up to at least 12288 octets of
+base64-encoded text. The default value is therefore also the minimum value
+accepted for this parameter.</p>
+
+<p> This feature is available in Postfix 3.4 and later. Prior versions use
+"<a href="postconf.5.html#line_length_limit">line_length_limit</a>", which may need to be raised to accommodate larger client
+responses, as may be needed with GSSAPI authentication of Windows AD users
+who are members of many groups. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sasl_security_options">smtpd_sasl_security_options</a>
+(default: noanonymous)</b></DT><DD>
+
+<p> Postfix SMTP server SASL security options; as of Postfix 2.3
+the list of available
+features depends on the SASL server implementation that is selected
+with <b><a href="postconf.5.html#smtpd_sasl_type">smtpd_sasl_type</a></b>. </p>
+
+<p> The following security features are defined for the <b>cyrus</b>
+server SASL implementation: </p>
+
+<p>
+Restrict what authentication mechanisms the Postfix SMTP server
+will offer to the client. The list of available authentication
+mechanisms is system dependent.
+</p>
+
+<p>
+Specify zero or more of the following:
+</p>
+
+<dl>
+
+<dt><b>noplaintext</b></dt>
+
+<dd>Disallow methods that use plaintext passwords. </dd>
+
+<dt><b>noactive</b></dt>
+
+<dd>Disallow methods subject to active (non-dictionary) attack. </dd>
+
+<dt><b>nodictionary</b></dt>
+
+<dd>Disallow methods subject to passive (dictionary) attack. </dd>
+
+<dt><b>noanonymous</b></dt>
+
+<dd>Disallow methods that allow anonymous authentication. </dd>
+
+<dt><b>forward_secrecy</b></dt>
+
+<dd>Only allow methods that support forward secrecy (Dovecot only).
+</dd>
+
+<dt><b>mutual_auth</b></dt>
+
+<dd>Only allow methods that provide mutual authentication (not available
+with Cyrus SASL version 1). </dd>
+
+</dl>
+
+<p>
+By default, the Postfix SMTP server accepts plaintext passwords but
+not anonymous logins.
+</p>
+
+<p>
+Warning: it appears that clients try authentication methods in the
+order as advertised by the server (e.g., PLAIN ANONYMOUS CRAM-MD5)
+which means that if you disable plaintext passwords, clients will
+log in anonymously, even when they should be able to use CRAM-MD5.
+So, if you disable plaintext logins, disable anonymous logins too.
+Postfix treats anonymous login as no authentication.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_sasl_security_options">smtpd_sasl_security_options</a> = noanonymous, noplaintext
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sasl_service">smtpd_sasl_service</a>
+(default: smtp)</b></DT><DD>
+
+<p> The service name that is passed to the SASL plug-in that is
+selected with <b><a href="postconf.5.html#smtpd_sasl_type">smtpd_sasl_type</a></b> and <b><a href="postconf.5.html#smtpd_sasl_path">smtpd_sasl_path</a></b>.
+</p>
+
+<p> This feature is available in Postfix 2.11 and later. Prior
+versions behave as if "<b>smtp</b>" is specified. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sasl_tls_security_options">smtpd_sasl_tls_security_options</a>
+(default: $<a href="postconf.5.html#smtpd_sasl_security_options">smtpd_sasl_security_options</a>)</b></DT><DD>
+
+<p> The SASL authentication security options that the Postfix SMTP
+server uses for TLS encrypted SMTP sessions. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sasl_type">smtpd_sasl_type</a>
+(default: cyrus)</b></DT><DD>
+
+<p> The SASL plug-in type that the Postfix SMTP server should use
+for authentication. The available types are listed with the
+"<b>postconf -a</b>" command. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sender_login_maps">smtpd_sender_login_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional lookup table with the SASL login names that own the sender
+(MAIL FROM) addresses.
+</p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found. With lookups from
+indexed files such as DB or DBM, or from networked tables such as
+NIS, LDAP or SQL, the following search operations are done with a
+sender address of <i>user@domain</i>: </p>
+
+<dl>
+
+<dt> 1) <i>user@domain</i> </dt>
+
+<dd>This table lookup is always done and has the highest precedence. </dd>
+
+<dt> 2) <i>user</i> </dt>
+
+<dd>This table lookup is done only when the <i>domain</i> part of the
+sender address matches $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
+or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>. </dd>
+
+<dt> 3) <i>@domain</i> </dt>
+
+<dd>This table lookup is done last and has the lowest precedence. </dd>
+
+</dl>
+
+<p>
+In all cases the result of table lookup must be either "not found"
+or a list of SASL login names separated by comma and/or whitespace.
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_sender_restrictions">smtpd_sender_restrictions</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional restrictions that the Postfix SMTP server applies in the
+context of a client MAIL FROM command.
+See <a href="SMTPD_ACCESS_README.html">SMTPD_ACCESS_README</a>, section "Delayed evaluation of SMTP access
+restriction lists" for a discussion of evaluation context and time.
+</p>
+
+<p>
+The default is to permit everything.
+</p>
+
+<p>
+Specify a list of restrictions, separated by commas and/or whitespace.
+Continue long lines by starting the next line with whitespace.
+Restrictions are applied in the order as specified; the first
+restriction that matches wins.
+</p>
+
+<p>
+The following restrictions are specific to the sender address
+received with the MAIL FROM command.
+</p>
+
+<dl>
+
+<dt><b><a name="check_sender_access">check_sender_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the MAIL FROM
+address, domain, parent domains, or localpart@, and execute the
+corresponding action. </dd>
+
+<dt><b><a name="check_sender_a_access">check_sender_a_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the IP addresses for
+the MAIL FROM domain, and execute the corresponding action. Note:
+a result of "OK" is not allowed for safety reasons. Instead, use
+DUNNO in order to exclude specific hosts from blacklists. This
+feature is available in Postfix 3.0 and later. </dd>
+
+<dt><b><a name="check_sender_mx_access">check_sender_mx_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the MX hosts for
+the MAIL FROM domain, and execute the corresponding action. Note:
+a result of "OK" is not allowed for safety reasons. Instead, use
+DUNNO in order to exclude specific hosts from blacklists. This
+feature is available in Postfix 2.1 and later. </dd>
+
+<dt><b><a name="check_sender_ns_access">check_sender_ns_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>
+
+<dd>Search the specified <a href="access.5.html">access(5)</a> database for the DNS servers
+for the MAIL FROM domain, and execute the corresponding action.
+Note: a result of "OK" is not allowed for safety reasons. Instead,
+use DUNNO in order to exclude specific hosts from blacklists. This
+feature is available in Postfix 2.1 and later. </dd>
+
+<dt><b><a name="reject_authenticated_sender_login_mismatch">reject_authenticated_sender_login_mismatch</a></b></dt>
+
+<dd>Enforces the <a href="postconf.5.html#reject_sender_login_mismatch">reject_sender_login_mismatch</a> restriction for
+authenticated clients only. This feature is available in
+Postfix version 2.1 and later. </dd>
+
+<dt><b><a name="reject_known_sender_login_mismatch">reject_known_sender_login_mismatch</a></b></dt>
+
+<dd>Apply the <a href="postconf.5.html#reject_sender_login_mismatch">reject_sender_login_mismatch</a> restriction only to MAIL
+FROM addresses that are known in $<a href="postconf.5.html#smtpd_sender_login_maps">smtpd_sender_login_maps</a>. This
+feature is available in Postfix version 2.11 and later. </dd>
+
+<dt><b><a name="reject_non_fqdn_sender">reject_non_fqdn_sender</a></b></dt>
+
+<dd>Reject the request when the MAIL FROM address specifies a
+domain that is not in
+fully-qualified domain form as required by the RFC. <br> The
+<a href="postconf.5.html#non_fqdn_reject_code">non_fqdn_reject_code</a> parameter specifies the response code for
+rejected requests (default: 504). </dd>
+
+<dt><b><a name="reject_rhsbl_sender">reject_rhsbl_sender <i>rbl_domain=d.d.d.d</i></a></b></dt>
+
+<dd>Reject the request when the MAIL FROM domain is listed with
+the A record "<i>d.d.d.d</i>" under <i>rbl_domain</i> (Postfix
+version 2.1 and later only). Each "<i>d</i>" is a number, or a
+pattern inside "[]" that contains one or more ";"-separated numbers
+or number..number ranges (Postfix version 2.8 and later). If no
+"<i>=d.d.d.d</i>" is specified,
+reject the request when the MAIL FROM domain is
+listed with any A record under <i>rbl_domain</i>. <br> The
+<a href="postconf.5.html#maps_rbl_reject_code">maps_rbl_reject_code</a> parameter specifies the response code for
+rejected requests (default: 554); the <a href="postconf.5.html#default_rbl_reply">default_rbl_reply</a> parameter
+specifies the default server reply; and the <a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a> parameter
+specifies tables with server replies indexed by <i>rbl_domain</i>.
+This feature is available in Postfix 2.0 and later.</dd>
+
+<dt><b><a name="reject_sender_login_mismatch">reject_sender_login_mismatch</a></b></dt>
+
+<dd>Reject the request when $<a href="postconf.5.html#smtpd_sender_login_maps">smtpd_sender_login_maps</a> specifies an
+owner for the MAIL FROM address, but the client is not (SASL) logged
+in as that MAIL FROM address owner; or when the client is (SASL)
+logged in, but the client login name doesn't own the MAIL FROM
+address according to $<a href="postconf.5.html#smtpd_sender_login_maps">smtpd_sender_login_maps</a>.</dd>
+
+<dt><b><a name="reject_unauthenticated_sender_login_mismatch">reject_unauthenticated_sender_login_mismatch</a></b></dt>
+
+<dd>Enforces the <a href="postconf.5.html#reject_sender_login_mismatch">reject_sender_login_mismatch</a> restriction for
+unauthenticated clients only. This feature is available in
+Postfix version 2.1 and later. </dd>
+
+<dt><b><a name="reject_unknown_sender_domain">reject_unknown_sender_domain</a></b></dt>
+
+<dd>Reject the request when Postfix is not final destination for
+the sender address, and the MAIL FROM domain has 1) no DNS MX and
+no DNS A
+record, or 2) a malformed MX record such as a record with
+a zero-length MX hostname (Postfix version 2.3 and later). <br> The
+reply is specified with the <a href="postconf.5.html#unknown_address_reject_code">unknown_address_reject_code</a> parameter
+(default: 450), <a href="postconf.5.html#unknown_address_tempfail_action">unknown_address_tempfail_action</a> (default:
+<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>), or 550 (nullmx, Postfix 3.0 and
+later). See the respective parameter descriptions for details.
+</dd>
+
+<dt><b><a name="reject_unlisted_sender">reject_unlisted_sender</a></b></dt>
+
+<dd>Reject the request when the MAIL FROM address is not listed in
+the list of valid recipients for its domain class. See the
+<a href="postconf.5.html#smtpd_reject_unlisted_sender">smtpd_reject_unlisted_sender</a> parameter description for details.
+This feature is available in Postfix 2.1 and later.</dd>
+
+<dt><b><a name="reject_unverified_sender">reject_unverified_sender</a></b></dt>
+
+<dd>Reject the request when mail to the MAIL FROM address is known to
+bounce, or when the sender address destination is not reachable.
+Address verification information is managed by the <a href="verify.8.html">verify(8)</a> server;
+see the <a href="ADDRESS_VERIFICATION_README.html">ADDRESS_VERIFICATION_README</a> file for details. <br> The
+<a href="postconf.5.html#unverified_sender_reject_code">unverified_sender_reject_code</a> parameter specifies the numerical
+response code when an address is known to bounce (default: 450,
+change into 550 when you are confident that it is safe to do so).
+<br>The <a href="postconf.5.html#unverified_sender_defer_code">unverified_sender_defer_code</a> specifies the numerical response
+code when an address probe failed due to a temporary problem
+(default: 450). <br> The <a href="postconf.5.html#unverified_sender_tempfail_action">unverified_sender_tempfail_action</a> parameter
+specifies the action after address probe failure due to a temporary
+problem (default: <a href="postconf.5.html#defer_if_permit">defer_if_permit</a>). <br> This feature breaks for
+aliased addresses with "<a href="postconf.5.html#enable_original_recipient">enable_original_recipient</a> = no" (Postfix
+&le; 3.2). <br> This feature is available in Postfix 2.1 and later.
+</dd>
+
+</dl>
+
+<p>
+Other restrictions that are valid in this context:
+</p>
+
+<ul>
+
+<li> <a href="#generic">Generic</a> restrictions that can be used
+in any SMTP command context, described under <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>.
+
+<li> SMTP command specific restrictions described under
+<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> and <a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>.
+
+<li> SMTP command specific restrictions described under
+<a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>. When recipient restrictions are listed
+under <a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a>, they have effect only with
+"<a href="postconf.5.html#smtpd_delay_reject">smtpd_delay_reject</a> = yes", so that $<a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a> is
+evaluated at the time of the RCPT TO command.
+
+</ul>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a> = <a href="postconf.5.html#reject_unknown_sender_domain">reject_unknown_sender_domain</a>
+<a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a> = <a href="postconf.5.html#reject_unknown_sender_domain">reject_unknown_sender_domain</a>,
+ <a href="postconf.5.html#check_sender_access">check_sender_access</a> <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/access
+</pre>
+
+
+</DD>
+
+<DT><b><a name="smtpd_service_name">smtpd_service_name</a>
+(default: smtpd)</b></DT><DD>
+
+<p> The internal service that <a href="postscreen.8.html">postscreen(8)</a> hands off allowed
+connections to. In a future version there may be different
+classes of SMTP service. </p>
+
+<p> This feature is available in Postfix 2.8. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_soft_error_limit">smtpd_soft_error_limit</a>
+(default: 10)</b></DT><DD>
+
+<p>
+The number of errors a remote SMTP client is allowed to make without
+delivering mail before the Postfix SMTP server slows down all its
+responses.
+</p>
+
+<ul>
+
+<li><p>With Postfix version 2.1 and later, the Postfix SMTP server
+delays all responses by $<a href="postconf.5.html#smtpd_error_sleep_time">smtpd_error_sleep_time</a> seconds. </p>
+
+<li><p>With Postfix versions 2.0 and earlier, the Postfix SMTP
+server delays all responses by (number of errors) seconds. </p>
+
+</ul>
+
+
+</DD>
+
+<DT><b><a name="smtpd_starttls_timeout">smtpd_starttls_timeout</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The time limit for Postfix SMTP server write and read operations
+during TLS startup and shutdown handshake procedures. The current
+default value is stress-dependent. Before Postfix version 2.8, it
+was fixed at 300s. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_timeout">smtpd_timeout</a>
+(default: normal: 300s, overload: 10s)</b></DT><DD>
+
+<p>
+The time limit for sending a Postfix SMTP server response and for
+receiving a remote SMTP client request. Normally the default limit
+is 300s, but it changes under overload to just 10s. With Postfix
+2.5 and earlier, the SMTP server always uses a time limit of 300s
+by default.
+</p>
+
+<p>
+Note: if you set SMTP time limits to very large values you may have
+to update the global <a href="postconf.5.html#ipc_timeout">ipc_timeout</a> parameter.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_CAfile">smtpd_tls_CAfile</a>
+(default: empty)</b></DT><DD>
+
+<p> A file containing (PEM format) CA certificates of root CAs trusted
+to sign either remote SMTP client certificates or intermediate CA
+certificates. These are loaded into memory before the <a href="smtpd.8.html">smtpd(8)</a> server
+enters the chroot jail. If the number of trusted roots is large, consider
+using <a href="postconf.5.html#smtpd_tls_CApath">smtpd_tls_CApath</a> instead, but note that the latter directory must
+be present in the chroot jail if the <a href="smtpd.8.html">smtpd(8)</a> server is chrooted. This
+file may also be used to augment the server certificate trust chain,
+but it is best to include all the required certificates directly in the
+server certificate file. </p>
+
+<p> Specify "<a href="postconf.5.html#smtpd_tls_CAfile">smtpd_tls_CAfile</a> = /path/to/system_CA_file" to use ONLY
+the system-supplied default Certification Authority certificates.
+</p>
+
+<p> Specify "<a href="postconf.5.html#tls_append_default_CA">tls_append_default_CA</a> = no" to prevent Postfix from
+appending the system-supplied default CAs and trusting third-party
+certificates. </p>
+
+<p> By default (see <a href="postconf.5.html#smtpd_tls_ask_ccert">smtpd_tls_ask_ccert</a>), client certificates are not
+requested, and <a href="postconf.5.html#smtpd_tls_CAfile">smtpd_tls_CAfile</a> should remain empty. If you do make use
+of client certificates, the distinguished names (DNs) of the Certification
+Authorities listed in <a href="postconf.5.html#smtpd_tls_CAfile">smtpd_tls_CAfile</a> are sent to the remote SMTP client
+in the client certificate request message. MUAs with multiple client
+certificates may use the list of preferred Certification Authorities
+to select the correct client certificate. You may want to put your
+"preferred" CA or CAs in this file, and install other trusted CAs in
+$<a href="postconf.5.html#smtpd_tls_CApath">smtpd_tls_CApath</a>. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtpd_tls_CAfile">smtpd_tls_CAfile</a> = /etc/postfix/CAcert.pem
+</pre>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_CApath">smtpd_tls_CApath</a>
+(default: empty)</b></DT><DD>
+
+<p> A directory containing (PEM format) CA certificates of root CAs
+trusted to sign either remote SMTP client certificates or intermediate CA
+certificates. Do not forget to create the necessary "hash" links with,
+for example, "$OPENSSL_HOME/bin/c_rehash /etc/postfix/certs". To use
+<a href="postconf.5.html#smtpd_tls_CApath">smtpd_tls_CApath</a> in chroot mode, this directory (or a copy) must be
+inside the chroot jail. </p>
+
+<p> Specify "<a href="postconf.5.html#smtpd_tls_CApath">smtpd_tls_CApath</a> = /path/to/system_CA_directory" to
+use ONLY the system-supplied default Certification Authority certificates.
+</p>
+
+<p> Specify "<a href="postconf.5.html#tls_append_default_CA">tls_append_default_CA</a> = no" to prevent Postfix from
+appending the system-supplied default CAs and trusting third-party
+certificates. </p>
+
+<p> By default (see <a href="postconf.5.html#smtpd_tls_ask_ccert">smtpd_tls_ask_ccert</a>), client certificates are
+not requested, and <a href="postconf.5.html#smtpd_tls_CApath">smtpd_tls_CApath</a> should remain empty. In contrast
+to <a href="postconf.5.html#smtpd_tls_CAfile">smtpd_tls_CAfile</a>, DNs of Certification Authorities installed
+in $<a href="postconf.5.html#smtpd_tls_CApath">smtpd_tls_CApath</a> are not included in the client certificate
+request message. MUAs with multiple client certificates may use the
+list of preferred Certification Authorities to select the correct
+client certificate. You may want to put your "preferred" CA or
+CAs in $<a href="postconf.5.html#smtpd_tls_CAfile">smtpd_tls_CAfile</a>, and install the remaining trusted CAs in
+$<a href="postconf.5.html#smtpd_tls_CApath">smtpd_tls_CApath</a>. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtpd_tls_CApath">smtpd_tls_CApath</a> = /etc/postfix/certs
+</pre>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_always_issue_session_ids">smtpd_tls_always_issue_session_ids</a>
+(default: yes)</b></DT><DD>
+
+<p> Force the Postfix SMTP server to issue a TLS session id, even
+when TLS session caching is turned off (<a href="postconf.5.html#smtpd_tls_session_cache_database">smtpd_tls_session_cache_database</a>
+is empty). This behavior is compatible with Postfix &lt; 2.3. </p>
+
+<p> With Postfix 2.3 and later the Postfix SMTP server can disable
+session id generation when TLS session caching is turned off. This
+keeps remote SMTP clients from caching sessions that almost certainly cannot
+be re-used. </p>
+
+<p> By default, the Postfix SMTP server always generates TLS session
+ids. This works around a known defect in mail client applications
+such as MS Outlook, and may also prevent interoperability issues
+with other MTAs. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtpd_tls_always_issue_session_ids">smtpd_tls_always_issue_session_ids</a> = no
+</pre>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_ask_ccert">smtpd_tls_ask_ccert</a>
+(default: no)</b></DT><DD>
+
+<p> Ask a remote SMTP client for a client certificate. This
+information is needed for certificate based mail relaying with,
+for example, the <a href="postconf.5.html#permit_tls_clientcerts">permit_tls_clientcerts</a> feature. </p>
+
+<p> Some clients such as Netscape will either complain if no
+certificate is available (for the list of CAs in $<a href="postconf.5.html#smtpd_tls_CAfile">smtpd_tls_CAfile</a>)
+or will offer multiple client certificates to choose from. This
+may be annoying, so this option is "off" by default. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_auth_only">smtpd_tls_auth_only</a>
+(default: no)</b></DT><DD>
+
+<p> When TLS encryption is optional in the Postfix SMTP server, do
+not announce or accept SASL authentication over unencrypted
+connections. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_ccert_verifydepth">smtpd_tls_ccert_verifydepth</a>
+(default: 9)</b></DT><DD>
+
+<p> The verification depth for remote SMTP client certificates. A
+depth of 1 is sufficient if the issuing CA is listed in a local CA
+file. </p>
+
+<p> The default verification depth is 9 (the OpenSSL default) for
+compatibility with earlier Postfix behavior. Prior to Postfix 2.5,
+the default value was 5, but the limit was not actually enforced. If
+you have set this to a lower non-default value, certificates with longer
+trust chains may now fail to verify. Certificate chains with 1 or 2
+CAs are common, deeper chains are more rare and any number between 5
+and 9 should suffice in practice. You can choose a lower number if,
+for example, you trust certificates directly signed by an issuing CA
+but not any CAs it delegates to. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_cert_file">smtpd_tls_cert_file</a>
+(default: empty)</b></DT><DD>
+
+<p> File with the Postfix SMTP server RSA certificate in PEM format.
+This file may also contain the Postfix SMTP server private RSA key.
+With Postfix &ge; 3.4 the preferred way to configure server keys and
+certificates is via the "<a href="postconf.5.html#smtpd_tls_chain_files">smtpd_tls_chain_files</a>" parameter. </p>
+
+<p> Public Internet MX hosts without certificates signed by a "reputable"
+CA must generate, and be prepared to present to most clients, a
+self-signed or private-CA signed certificate. The client will not be
+able to authenticate the server, but unless it is running Postfix 2.3 or
+similar software, it will still insist on a server certificate. </p>
+
+<p> For servers that are <b>not</b> public Internet MX hosts, Postfix
+supports configurations with no certificates. This entails the use of
+just the anonymous TLS ciphers, which are not supported by typical SMTP
+clients. Since some clients may not fall back to plain text after a TLS
+handshake failure, a certificate-less Postfix SMTP server will be unable
+to receive email from some TLS-enabled clients. To avoid accidental
+configurations with no certificates, Postfix enables certificate-less
+operation only when the administrator explicitly sets
+"<a href="postconf.5.html#smtpd_tls_cert_file">smtpd_tls_cert_file</a> = none". This ensures that new Postfix SMTP server
+configurations will not accidentally enable TLS without certificates. </p>
+
+<p> Note that server certificates are not optional in TLS 1.3. To run
+without certificates you'd have to disable the TLS 1.3 protocol by
+including '!TLSv1.3' in "<a href="postconf.5.html#smtpd_tls_protocols">smtpd_tls_protocols</a>" and perhaps also
+"<a href="postconf.5.html#smtpd_tls_mandatory_protocols">smtpd_tls_mandatory_protocols</a>". It is simpler instead to just
+configure a certificate chain. Certificate-less operation is not
+recommended. <p>
+
+<p> Both RSA and DSA certificates are supported. When both types
+are present, the cipher used determines which certificate will be
+presented to the client. For Netscape and OpenSSL clients without
+special cipher choices the RSA certificate is preferred. </p>
+
+<p> To enable a remote SMTP client to verify the Postfix SMTP server
+certificate, the issuing CA certificates must be made available to the
+client. You should include the required certificates in the server
+certificate file, the server certificate first, then the issuing
+CA(s) (bottom-up order). </p>
+
+<p> Example: the certificate for "server.example.com" was issued by
+"intermediate CA" which itself has a certificate of "root CA".
+Create the server.pem file with "cat server_cert.pem intermediate_CA.pem
+root_CA.pem &gt; server.pem". </p>
+
+<p> If you also want to verify client certificates issued by these
+CAs, you can add the CA certificates to the <a href="postconf.5.html#smtpd_tls_CAfile">smtpd_tls_CAfile</a>, in which
+case it is not necessary to have them in the <a href="postconf.5.html#smtpd_tls_cert_file">smtpd_tls_cert_file</a>,
+<a href="postconf.5.html#smtpd_tls_dcert_file">smtpd_tls_dcert_file</a> (obsolete) or <a href="postconf.5.html#smtpd_tls_eccert_file">smtpd_tls_eccert_file</a>. </p>
+
+<p> A certificate supplied here must be usable as an SSL server certificate
+and hence pass the "openssl verify -purpose sslserver ..." test. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtpd_tls_cert_file">smtpd_tls_cert_file</a> = /etc/postfix/server.pem
+</pre>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_chain_files">smtpd_tls_chain_files</a>
+(default: empty)</b></DT><DD>
+
+<p> List of one or more PEM files, each holding one or more private keys
+directly followed by a corresponding certificate chain. The file names
+are separated by commas and/or whitespace. This parameter obsoletes the
+legacy algorithm-specific key and certificate file settings. When this
+parameter is non-empty, the legacy parameters are ignored, and a warning
+is logged if any are also non-empty. </p>
+
+<p> With the proliferation of multiple private key algorithms&mdash;which,
+as of OpenSSL 1.1.1, include DSA (obsolete), RSA, ECDSA, Ed25519
+and Ed448&mdash;it is increasingly impractical to use separate
+parameters to configure the key and certificate chain for each
+algorithm. Therefore, Postfix now supports storing multiple keys and
+corresponding certificate chains in a single file or in a set of files.
+
+<p> Each key must appear <b>immediately before</b> the corresponding
+certificate, optionally followed by additional issuer certificates that
+complete the certificate chain for that key. When multiple files are
+specified, they are equivalent to a single file that is concatenated
+from those files in the given order. Thus, while a key must always
+precede its certificate and issuer chain, it can be in a separate file,
+so long as that file is listed immediately before the file that holds
+the corresponding certificate chain. Once all the files are
+concatenated, the sequence of PEM objects must be: <i>key1, cert1,
+[chain1], key2, cert2, [chain2], ..., keyN, certN, [chainN].</i> </p>
+
+<p> Storing the private key in the same file as the corresponding
+certificate is more reliable. With the key and certificate in separate
+files, there is a chance that during key rollover a Postfix process
+might load a private key and certificate from separate files that don't
+match. Various operational errors may even result in a persistent
+broken configuration in which the certificate does not match the private
+key. </p>
+
+<p> The file or files must contain at most one key of each type. If,
+for example, two or more RSA keys and corresponding chains are listed,
+depending on the version of OpenSSL either only the last one will be
+used or an configuration error may be detected. Note that while
+"Ed25519" and "Ed448" are considered separate algorithms, the various
+ECDSA curves (typically one of prime256v1, secp384r1 or secp521r1) are
+considered as different parameters of a single "ECDSA" algorithm, so it
+is not presently possible to configure keys for more than one ECDSA
+curve. </p>
+
+<p> RSA is still the most widely supported algorithm. Presently (late
+2018), ECDSA support is common, but not yet universal, and Ed25519 and
+Ed448 support is mostly absent. Therefore, an RSA key should generally
+be configured, along with any additional keys for the other algorithms
+when desired. </p>
+
+<p>
+Example (separate files for each key and corresponding certificate chain):
+</p>
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtpd_tls_chain_files">smtpd_tls_chain_files</a> =
+ ${<a href="postconf.5.html#config_directory">config_directory</a>}/ed25519.pem,
+ ${<a href="postconf.5.html#config_directory">config_directory</a>}/ed448.pem,
+ ${<a href="postconf.5.html#config_directory">config_directory</a>}/rsa.pem
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/ed25519.pem:
+ -----BEGIN PRIVATE KEY-----
+ MC4CAQAwBQYDK2VwBCIEIEJfbbO4BgBQGBg9NAbIJaDBqZb4bC4cOkjtAH+Efbz3
+ -----END PRIVATE KEY-----
+ -----BEGIN CERTIFICATE-----
+ MIIBKzCB3qADAgECAhQaw+rflRreYuUZBp0HuNn/e5rMZDAFBgMrZXAwFDESMBAG
+ ...
+ nC0egv51YPDWxEHom4QA
+ -----END CERTIFICATE-----
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/ed448.pem:
+ -----BEGIN PRIVATE KEY-----
+ MEcCAQAwBQYDK2VxBDsEOQf+m0P+G0qi+NZ0RolyeiE5zdlPQR8h8y4jByBifpIe
+ LNler7nzHQJ1SLcOiXFHXlxp/84VZuh32A==
+ -----END PRIVATE KEY-----
+ -----BEGIN CERTIFICATE-----
+ MIIBdjCB96ADAgECAhQSv4oP972KypOZPNPF4fmsiQoRHzAFBgMrZXEwFDESMBAG
+ ...
+ pQcWsx+4J29e6YWH3Cy/CdUaexKP4RPCZDrPX7bk5C2BQ+eeYOxyThMA
+ -----END CERTIFICATE-----
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/rsa.pem:
+ -----BEGIN PRIVATE KEY-----
+ MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDc4QusgkahH9rL
+ ...
+ ahQkZ3+krcaJvDSMgvu0tDc=
+ -----END PRIVATE KEY-----
+ -----BEGIN CERTIFICATE-----
+ MIIC+DCCAeCgAwIBAgIUIUkrbk1GAemPCT8i9wKsTGDH7HswDQYJKoZIhvcNAQEL
+ ...
+ Rirz15HGVNTK8wzFd+nulPzwUo6dH2IU8KazmyRi7OGvpyrMlm15TRE2oyE=
+ -----END CERTIFICATE-----
+</pre>
+</blockquote>
+
+<p>
+Example (all keys and certificates in a single file):
+</p>
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtpd_tls_chain_files">smtpd_tls_chain_files</a> = ${<a href="postconf.5.html#config_directory">config_directory</a>}/chains.pem
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/chains.pem:
+ -----BEGIN PRIVATE KEY-----
+ MC4CAQAwBQYDK2VwBCIEIEJfbbO4BgBQGBg9NAbIJaDBqZb4bC4cOkjtAH+Efbz3
+ -----END PRIVATE KEY-----
+ -----BEGIN CERTIFICATE-----
+ MIIBKzCB3qADAgECAhQaw+rflRreYuUZBp0HuNn/e5rMZDAFBgMrZXAwFDESMBAG
+ ...
+ nC0egv51YPDWxEHom4QA
+ -----END CERTIFICATE-----
+ -----BEGIN PRIVATE KEY-----
+ MEcCAQAwBQYDK2VxBDsEOQf+m0P+G0qi+NZ0RolyeiE5zdlPQR8h8y4jByBifpIe
+ LNler7nzHQJ1SLcOiXFHXlxp/84VZuh32A==
+ -----END PRIVATE KEY-----
+ -----BEGIN CERTIFICATE-----
+ MIIBdjCB96ADAgECAhQSv4oP972KypOZPNPF4fmsiQoRHzAFBgMrZXEwFDESMBAG
+ ...
+ pQcWsx+4J29e6YWH3Cy/CdUaexKP4RPCZDrPX7bk5C2BQ+eeYOxyThMA
+ -----END CERTIFICATE-----
+ -----BEGIN PRIVATE KEY-----
+ MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDc4QusgkahH9rL
+ ...
+ ahQkZ3+krcaJvDSMgvu0tDc=
+ -----END PRIVATE KEY-----
+ -----BEGIN CERTIFICATE-----
+ MIIC+DCCAeCgAwIBAgIUIUkrbk1GAemPCT8i9wKsTGDH7HswDQYJKoZIhvcNAQEL
+ ...
+ Rirz15HGVNTK8wzFd+nulPzwUo6dH2IU8KazmyRi7OGvpyrMlm15TRE2oyE=
+ -----END CERTIFICATE-----
+</pre>
+</blockquote>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_cipherlist">smtpd_tls_cipherlist</a>
+(default: empty)</b></DT><DD>
+
+<p> Obsolete Postfix &lt; 2.3 control for the Postfix SMTP server TLS
+cipher list. It is easy to create interoperability problems by choosing
+a non-default cipher list. Do not use a non-default TLS cipherlist for
+MX hosts on the public Internet. Clients that begin the TLS handshake,
+but are unable to agree on a common cipher, may not be able to send any
+email to the SMTP server. Using a restricted cipher list may be more
+appropriate for a dedicated MSA or an internal mailhub, where one can
+exert some control over the TLS software and settings of the connecting
+clients. </p>
+
+<p> <b>Note:</b> do not use "" quotes around the parameter value. </p>
+
+<p>This feature is available with Postfix version 2.2. It is not used with
+Postfix 2.3 and later; use <a href="postconf.5.html#smtpd_tls_mandatory_ciphers">smtpd_tls_mandatory_ciphers</a> instead. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_ciphers">smtpd_tls_ciphers</a>
+(default: medium)</b></DT><DD>
+
+<p> The minimum TLS cipher grade that the Postfix SMTP server
+will use with opportunistic TLS encryption. Cipher types listed in
+<a href="postconf.5.html#smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a> are excluded from the base definition of
+the selected cipher grade. The default value is "medium" for Postfix
+releases after the middle of 2015, "export" for older releases.
+</p>
+
+<p> When TLS is mandatory the cipher grade is chosen via the
+<a href="postconf.5.html#smtpd_tls_mandatory_ciphers">smtpd_tls_mandatory_ciphers</a> configuration parameter, see there for syntax
+details. </p>
+
+<p> This feature is available in Postfix 2.6 and later. With earlier Postfix
+releases only the <a href="postconf.5.html#smtpd_tls_mandatory_ciphers">smtpd_tls_mandatory_ciphers</a> parameter is implemented,
+and opportunistic TLS always uses "export" or better (i.e. all) ciphers. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_dcert_file">smtpd_tls_dcert_file</a>
+(default: empty)</b></DT><DD>
+
+<p> File with the Postfix SMTP server DSA certificate in PEM format.
+This file may also contain the Postfix SMTP server private DSA key.
+The DSA algorithm is obsolete and should not be used. </p>
+
+<p> See the discussion under <a href="postconf.5.html#smtpd_tls_cert_file">smtpd_tls_cert_file</a> for more details.
+</p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtpd_tls_dcert_file">smtpd_tls_dcert_file</a> = /etc/postfix/server-dsa.pem
+</pre>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_dh1024_param_file">smtpd_tls_dh1024_param_file</a>
+(default: empty)</b></DT><DD>
+
+<p> File with DH parameters that the Postfix SMTP server should
+use with non-export EDH ciphers. </p>
+
+<p> Instead of using the exact same parameter sets as distributed
+with other TLS packages, it is more secure to generate your own
+set of parameters with something like the following commands: </p>
+
+<blockquote>
+<pre>
+openssl dhparam -out /etc/postfix/dh512.pem 512
+openssl dhparam -out /etc/postfix/dh1024.pem 1024
+openssl dhparam -out /etc/postfix/dh2048.pem 2048
+</pre>
+</blockquote>
+
+<p> It is safe to share the same DH parameters between multiple
+Postfix instances. If you prefer, you can generate separate
+parameters for each instance. </p>
+
+<p> If you want to take maximal advantage of ciphers that offer <a
+href="FORWARD_SECRECY_README.html#dfn_fs">forward secrecy</a> see
+the <a href="FORWARD_SECRECY_README.html#quick-start">Getting
+started</a> section of <a
+href="FORWARD_SECRECY_README.html">FORWARD_SECRECY_README</a>. The
+full document conveniently presents all information about Postfix
+"perfect" forward secrecy support in one place: what forward secrecy
+is, how to tweak settings, and what you can expect to see when
+Postfix uses ciphers with forward secrecy. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtpd_tls_dh1024_param_file">smtpd_tls_dh1024_param_file</a> = /etc/postfix/dh2048.pem
+</pre>
+
+<p>This feature is available with Postfix version 2.2.</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_dh512_param_file">smtpd_tls_dh512_param_file</a>
+(default: empty)</b></DT><DD>
+
+<p> File with DH parameters that the Postfix SMTP server should
+use with export-grade EDH ciphers. The default SMTP server cipher
+grade is "medium" with Postfix releases after the middle of 2015,
+and as a result export-grade cipher suites are by default not used.
+</p>
+
+<p> See also the discussion under the <a href="postconf.5.html#smtpd_tls_dh1024_param_file">smtpd_tls_dh1024_param_file</a>
+configuration parameter. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtpd_tls_dh512_param_file">smtpd_tls_dh512_param_file</a> = /etc/postfix/dh_512.pem
+</pre>
+
+<p>This feature is available with Postfix version 2.2.</p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_dkey_file">smtpd_tls_dkey_file</a>
+(default: $<a href="postconf.5.html#smtpd_tls_dcert_file">smtpd_tls_dcert_file</a>)</b></DT><DD>
+
+<p> File with the Postfix SMTP server DSA private key in PEM format.
+This file may be combined with the Postfix SMTP server DSA certificate
+file specified with $<a href="postconf.5.html#smtpd_tls_dcert_file">smtpd_tls_dcert_file</a>. The DSA algorithm is obsolete
+and should not be used. </p>
+
+<p> The private key must be accessible without a pass-phrase, i.e. it
+must not be encrypted. File permissions should grant read-only
+access to the system superuser account ("root"), and no access
+to anyone else. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_eccert_file">smtpd_tls_eccert_file</a>
+(default: empty)</b></DT><DD>
+
+<p> File with the Postfix SMTP server ECDSA certificate in PEM format.
+This file may also contain the Postfix SMTP server private ECDSA key.
+With Postfix &ge; 3.4 the preferred way to configure server keys and
+certificates is via the "<a href="postconf.5.html#smtpd_tls_chain_files">smtpd_tls_chain_files</a>" parameter. </p>
+
+<p> See the discussion under <a href="postconf.5.html#smtpd_tls_cert_file">smtpd_tls_cert_file</a> for more details. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtpd_tls_eccert_file">smtpd_tls_eccert_file</a> = /etc/postfix/ecdsa-scert.pem
+</pre>
+
+<p> This feature is available in Postfix 2.6 and later, when Postfix is
+compiled and linked with OpenSSL 1.0.0 or later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_eckey_file">smtpd_tls_eckey_file</a>
+(default: $<a href="postconf.5.html#smtpd_tls_eccert_file">smtpd_tls_eccert_file</a>)</b></DT><DD>
+
+<p> File with the Postfix SMTP server ECDSA private key in PEM format.
+This file may be combined with the Postfix SMTP server ECDSA certificate
+file specified with $<a href="postconf.5.html#smtpd_tls_eccert_file">smtpd_tls_eccert_file</a>. With Postfix &ge; 3.4 the
+preferred way to configure server keys and certificates is via the
+"<a href="postconf.5.html#smtpd_tls_chain_files">smtpd_tls_chain_files</a>" parameter. </p>
+
+<p> The private key must be accessible without a pass-phrase, i.e. it
+must not be encrypted. File permissions should grant read-only
+access to the system superuser account ("root"), and no access
+to anyone else. </p>
+
+<p> This feature is available in Postfix 2.6 and later, when Postfix is
+compiled and linked with OpenSSL 1.0.0 or later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_eecdh_grade">smtpd_tls_eecdh_grade</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The Postfix SMTP server security grade for ephemeral elliptic-curve
+Diffie-Hellman (EECDH) key exchange. </p>
+
+<p> The available choices are: </p>
+
+<dl>
+
+<dt><b>none</b></dt> <dd> Don't use EECDH. Ciphers based on EECDH key
+exchange will be disabled. This is the default in Postfix versions
+2.6 and 2.7. </dd>
+
+<dt><b>strong</b></dt> <dd> Use EECDH with approximately 128
+bits of security at a reasonable computational cost. This is the
+current best-practice trade-off between security and computational
+efficiency. This is the default in Postfix version 2.8 and later.
+</dd>
+
+<dt><b>ultra</b></dt> <dd> Use EECDH with approximately 192 bits of
+security at computational cost that is approximately twice as high
+as 128 bit strength ECC. Barring significant progress in attacks on
+elliptic curve crypto-systems, the "strong" curve is sufficient for most
+users. </dd>
+
+<dt><b>auto</b></dt> <dd> Use the most preferred curve that is
+supported by both the client and the server. This setting requires
+Postfix &ge; 3.2 compiled and linked with OpenSSL &ge; 1.0.2. This
+is the default setting under the above conditions. </dd>
+
+</dl>
+
+<p> If you want to take maximal advantage of ciphers that offer <a
+href="FORWARD_SECRECY_README.html#dfn_fs">forward secrecy</a> see
+the <a href="FORWARD_SECRECY_README.html#quick-start">Getting
+started</a> section of <a
+href="FORWARD_SECRECY_README.html">FORWARD_SECRECY_README</a>. The
+full document conveniently presents all information about Postfix
+"perfect" forward secrecy support in one place: what forward secrecy
+is, how to tweak settings, and what you can expect to see when
+Postfix uses ciphers with forward secrecy. </p>
+
+<p> This feature is available in Postfix 2.6 and later, when it is
+compiled and linked with OpenSSL 1.0.0 or later on platforms
+where EC algorithms have not been disabled by the vendor. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a>
+(default: empty)</b></DT><DD>
+
+<p> List of ciphers or cipher types to exclude from the SMTP server
+cipher list at all TLS security levels. Excluding valid ciphers
+can create interoperability problems. DO NOT exclude ciphers unless it
+is essential to do so. This is not an OpenSSL cipherlist; it is a simple
+list separated by whitespace and/or commas. The elements are a single
+cipher, or one or more "+" separated cipher properties, in which case
+only ciphers matching <b>all</b> the properties are excluded. </p>
+
+<p> Examples (some of these will cause problems): </p>
+
+<blockquote>
+<pre>
+<a href="postconf.5.html#smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a> = aNULL
+<a href="postconf.5.html#smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a> = MD5, DES
+<a href="postconf.5.html#smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a> = DES+MD5
+<a href="postconf.5.html#smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a> = AES256-SHA, DES-CBC3-MD5
+<a href="postconf.5.html#smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a> = kEDH+aRSA
+</pre>
+</blockquote>
+
+<p> The first setting disables anonymous ciphers. The next setting
+disables ciphers that use the MD5 digest algorithm or the (single) DES
+encryption algorithm. The next setting disables ciphers that use MD5 and
+DES together. The next setting disables the two ciphers "AES256-SHA"
+and "DES-CBC3-MD5". The last setting disables ciphers that use "EDH"
+key exchange with RSA authentication. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a>
+(default: md5)</b></DT><DD>
+
+<p> The message digest algorithm to construct remote SMTP
+client-certificate
+fingerprints or public key fingerprints (Postfix 2.9 and later)
+for <b><a href="postconf.5.html#check_ccert_access">check_ccert_access</a></b> and <b><a href="postconf.5.html#permit_tls_clientcerts">permit_tls_clientcerts</a></b>. The
+default algorithm is <b>md5</b>, for backwards compatibility with Postfix
+releases prior to 2.5. </p>
+
+<p> Advances in hash
+function cryptanalysis have led to md5 being deprecated in favor of sha1.
+However, as long as there are no known "second pre-image" attacks
+against md5, its use in this context can still be considered safe.
+</p>
+
+<p> While additional digest algorithms are often available with OpenSSL's
+libcrypto, only those used by libssl in SSL cipher suites are available to
+Postfix. </p>
+
+<p> To find the fingerprint of a specific certificate file, with a
+specific digest algorithm, run: </p>
+
+<blockquote>
+<pre>
+$ openssl x509 -noout -fingerprint -<i>digest</i> -in <i>certfile</i>.pem
+</pre>
+</blockquote>
+
+<p> The text to the right of "=" sign is the desired fingerprint.
+For example: </p>
+
+<blockquote>
+<pre>
+$ openssl x509 -noout -fingerprint -sha1 -in cert.pem
+SHA1 Fingerprint=D4:6A:AB:19:24:79:F8:32:BB:A6:CB:66:82:C0:8E:9B:EE:29:A8:1A
+</pre>
+</blockquote>
+
+<p> To extract the public key fingerprint from an X.509 certificate,
+you need to extract the public key from the certificate and compute
+the appropriate digest of its DER (ASN.1) encoding. With OpenSSL
+the "-pubkey" option of the "x509" command extracts the public
+key always in "PEM" format. We pipe the result to another OpenSSL
+command that converts the key to DER and then to the "dgst" command
+to compute the fingerprint. </p>
+
+<p> The actual command to transform the key to DER format depends
+on the version of OpenSSL used. With OpenSSL 1.0.0 and later, the
+"pkey" command supports all key types. With OpenSSL 0.9.8 and
+earlier, the key type is always RSA (nobody uses DSA, and EC
+keys are not fully supported by 0.9.8), so the "rsa" command is
+used. </p>
+<blockquote>
+<pre>
+# OpenSSL 1.0 with all certificates and SHA-1 fingerprints.
+$ openssl x509 -in cert.pem -noout -pubkey |
+ openssl pkey -pubin -outform DER |
+ openssl dgst -sha1 -c
+(stdin)= 64:3f:1f:f6:e5:1e:d4:2a:56:8b:fc:09:1a:61:98:b5:bc:7c:60:58
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+# OpenSSL 0.9.8 with RSA certificates and MD5 fingerprints.
+$ openssl x509 -in cert.pem -noout -pubkey |
+ openssl rsa -pubin -outform DER |
+ openssl dgst -md5 -c
+(stdin)= f4:62:60:f6:12:8f:d5:8d:28:4d:13:a7:db:b2:ff:50
+</pre>
+</blockquote>
+
+<p> The Postfix SMTP server and client log the peer (leaf) certificate
+fingerprint and public key fingerprint when the TLS loglevel is 2 or
+higher. </p>
+
+<p> <b>Note:</b> Postfix 2.9.0&ndash;2.9.5 computed the public key
+fingerprint incorrectly. To use public-key fingerprints, upgrade
+to Postfix 2.9.6 or later. </p>
+
+<p> Example: client-certificate access table, with sha1 fingerprints: </p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> = sha1
+ <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> =
+ <a href="postconf.5.html#check_ccert_access">check_ccert_access</a> <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/access,
+ reject
+</pre>
+<pre>
+/etc/postfix/access:
+ # Action folded to next line...
+ AF:88:7C:AD:51:95:6F:36:96:F6:01:FB:2E:48:CD:AB:49:25:A2:3B
+ OK
+ 85:16:78:FD:73:6E:CE:70:E0:31:5F:0D:3C:C8:6D:C4:2C:24:59:E1
+ <a href="postconf.5.html#permit_auth_destination">permit_auth_destination</a>
+</pre>
+</blockquote>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_key_file">smtpd_tls_key_file</a>
+(default: $<a href="postconf.5.html#smtpd_tls_cert_file">smtpd_tls_cert_file</a>)</b></DT><DD>
+
+<p> File with the Postfix SMTP server RSA private key in PEM format.
+This file may be combined with the Postfix SMTP server RSA certificate
+file specified with $<a href="postconf.5.html#smtpd_tls_cert_file">smtpd_tls_cert_file</a>. With Postfix &ge; 3.4 the
+preferred way to configure server keys and certificates is via the
+"<a href="postconf.5.html#smtpd_tls_chain_files">smtpd_tls_chain_files</a>" parameter. </p>
+
+<p> The private key must be accessible without a pass-phrase, i.e. it
+must not be encrypted. File permissions should grant read-only
+access to the system superuser account ("root"), and no access
+to anyone else. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_loglevel">smtpd_tls_loglevel</a>
+(default: 0)</b></DT><DD>
+
+<p> Enable additional Postfix SMTP server logging of TLS activity.
+Each logging level also includes the information that is logged at
+a lower logging level. </p>
+
+<dl compact>
+
+<dt> </dt> <dd> 0 Disable logging of TLS activity. </dd>
+
+<dt> </dt> <dd> 1 Log only a summary message on TLS handshake completion
+&mdash; no logging of client certificate trust-chain verification errors
+if client certificate verification is not required. With Postfix 2.8 and
+earlier, log the summary message, peer certificate summary information
+and unconditionally log trust-chain verification errors. </dd>
+
+<dt> </dt> <dd> 2 Also log levels during TLS negotiation. </dd>
+
+<dt> </dt> <dd> 3 Also log hexadecimal and ASCII dump of TLS negotiation
+process. </dd>
+
+<dt> </dt> <dd> 4 Also log hexadecimal and ASCII dump of complete
+transmission after STARTTLS. </dd>
+
+</dl>
+
+<p> Do not use "<a href="postconf.5.html#smtpd_tls_loglevel">smtpd_tls_loglevel</a> = 2" or higher except in case
+of problems. Use of loglevel 4 is strongly discouraged. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_mandatory_ciphers">smtpd_tls_mandatory_ciphers</a>
+(default: medium)</b></DT><DD>
+
+<p> The minimum TLS cipher grade that the Postfix SMTP server will
+use with mandatory TLS encryption. The default grade ("medium") is
+sufficiently strong that any benefit from globally restricting TLS
+sessions to a more stringent grade is likely negligible, especially
+given the fact that many implementations still do not offer any stronger
+("high" grade) ciphers, while those that do, will always use "high"
+grade ciphers. So insisting on "high" grade ciphers is generally
+counter-productive. Allowing "export" or "low" ciphers is typically
+not a good idea, as systems limited to just these are limited to
+obsolete browsers. No known SMTP clients fail to support at least
+one "medium" or "high" grade cipher. </p>
+
+<p> The following cipher grades are supported: </p>
+
+<dl>
+<dt><b>export</b></dt>
+<dd> Enable "EXPORT" grade or stronger OpenSSL ciphers. The
+underlying cipherlist is specified via the <a href="postconf.5.html#tls_export_cipherlist">tls_export_cipherlist</a>
+configuration parameter, which you are strongly encouraged to not
+change. This choice is insecure and SHOULD NOT be used. </dd>
+
+<dt><b>low</b></dt>
+<dd> Enable "LOW" grade or stronger OpenSSL ciphers. The underlying
+cipherlist is specified via the <a href="postconf.5.html#tls_low_cipherlist">tls_low_cipherlist</a> configuration
+parameter, which you are strongly encouraged to not change. This
+choice is insecure and SHOULD NOT be used. </dd>
+
+<dt><b>medium</b></dt>
+<dd> Enable "MEDIUM" grade or stronger OpenSSL ciphers. These use 128-bit
+or longer symmetric bulk-encryption keys. This is the default minimum
+strength for mandatory TLS encryption. The underlying cipherlist is
+specified via the <a href="postconf.5.html#tls_medium_cipherlist">tls_medium_cipherlist</a> configuration parameter, which
+you are strongly encouraged to not change. </dd>
+
+<dt><b>high</b></dt>
+<dd> Enable only "HIGH" grade OpenSSL ciphers. The
+underlying cipherlist is specified via the <a href="postconf.5.html#tls_high_cipherlist">tls_high_cipherlist</a>
+configuration parameter, which you are strongly encouraged to
+not change. </dd>
+
+<dt><b>null</b></dt>
+<dd> Enable only the "NULL" OpenSSL ciphers, these provide authentication
+without encryption. This setting is only appropriate in the rare
+case that all clients are prepared to use NULL ciphers (not normally
+enabled in TLS clients). The underlying cipherlist is specified via the
+<a href="postconf.5.html#tls_null_cipherlist">tls_null_cipherlist</a> configuration parameter, which you are strongly
+encouraged to not change. </dd>
+
+</dl>
+
+<p> Cipher types listed in
+<a href="postconf.5.html#smtpd_tls_mandatory_exclude_ciphers">smtpd_tls_mandatory_exclude_ciphers</a> or <a href="postconf.5.html#smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a> are
+excluded from the base definition of the selected cipher grade. See
+<a href="postconf.5.html#smtpd_tls_ciphers">smtpd_tls_ciphers</a> for cipher controls that apply to opportunistic
+TLS. </p>
+
+<p> The underlying cipherlists for grades other than "null" include
+anonymous ciphers, but these are automatically filtered out if the
+server is configured to ask for remote SMTP client certificates. You are very
+unlikely to need to take any steps to exclude anonymous ciphers, they
+are excluded automatically as required. If you must exclude anonymous
+ciphers even when Postfix does not need or use peer certificates, set
+"<a href="postconf.5.html#smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a> = aNULL". To exclude anonymous ciphers only
+when TLS is enforced, set "<a href="postconf.5.html#smtpd_tls_mandatory_exclude_ciphers">smtpd_tls_mandatory_exclude_ciphers</a> = aNULL". </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_mandatory_exclude_ciphers">smtpd_tls_mandatory_exclude_ciphers</a>
+(default: empty)</b></DT><DD>
+
+<p> Additional list of ciphers or cipher types to exclude from the
+Postfix SMTP server cipher list at mandatory TLS security levels.
+This list
+works in addition to the exclusions listed with <a href="postconf.5.html#smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a>
+(see there for syntax details). </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_mandatory_protocols">smtpd_tls_mandatory_protocols</a>
+(default: !SSLv2, !SSLv3)</b></DT><DD>
+
+<p> The SSL/TLS protocols accepted by the Postfix SMTP server with
+mandatory TLS encryption. If the list is empty, the server supports
+all available SSL/TLS protocol versions. A non-empty value is a
+list of protocol names separated by whitespace, commas or colons.
+The supported protocol names are "SSLv2", "SSLv3" and "TLSv1", and
+are not case sensitive. The default value is "!SSLv2, !SSLv3" for
+Postfix releases after the middle of 2015, "!SSLv2" for older
+releases. </p>
+
+<p> With Postfix &ge; 2.5 the parameter syntax was expanded to support
+protocol exclusions. One can explicitly exclude "SSLv2" by setting
+"<a href="postconf.5.html#smtpd_tls_mandatory_protocols">smtpd_tls_mandatory_protocols</a> = !SSLv2". To exclude both "SSLv2" and
+"SSLv3" set "<a href="postconf.5.html#smtpd_tls_mandatory_protocols">smtpd_tls_mandatory_protocols</a> = !SSLv2, !SSLv3". Listing
+the protocols to include, rather than protocols to exclude, is
+supported, but not recommended. The exclusion form more closely
+matches the underlying OpenSSL interface semantics. </p>
+
+<p> Note: As of OpenSSL 1.0.1 two new protocols are defined, "TLSv1.1"
+and "TLSv1.2". When Postfix &le; 2.5 is linked against OpenSSL 1.0.1
+or later, these, or any other new protocol versions, cannot be
+disabled. The latest patch levels of Postfix &ge; 2.6, and all
+versions of Postfix &ge; 2.10 can disable support for "TLSv1.1" or
+"TLSv1.2". </p>
+
+<p> OpenSSL 1.1.1 introduces support for "TLSv1.3". With Postfix
+&ge; 3.4 (or patch releases &ge; 3.0.14, 3.1.10, 3.2.7 and 3.3.2)
+this can be disabled, if need be, via "!TLSv1.3". </p>
+
+<p> Example: </p>
+
+<pre>
+# Preferred syntax with Postfix &ge; 2.5:
+<a href="postconf.5.html#smtpd_tls_mandatory_protocols">smtpd_tls_mandatory_protocols</a> = !SSLv2, !SSLv3
+# Legacy syntax:
+<a href="postconf.5.html#smtpd_tls_mandatory_protocols">smtpd_tls_mandatory_protocols</a> = TLSv1
+</pre>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_protocols">smtpd_tls_protocols</a>
+(default: !SSLv2, !SSLv3)</b></DT><DD>
+
+<p> List of TLS protocols that the Postfix SMTP server will exclude
+or include with opportunistic TLS encryption. The default value is
+"!SSLv2, !SSLv3" for Postfix releases after the middle of 2015,
+empty for older releases allowing all protocols to be
+used with opportunistic TLS. A non-empty value is a list of protocol
+names separated by whitespace, commas or colons. The supported
+protocol names are "SSLv2", "SSLv3" and "TLSv1", and are not case
+sensitive. </p>
+
+<p> Note: As of OpenSSL 1.0.1 two new protocols are defined, "TLSv1.1"
+and "TLSv1.2". The latest patch levels of Postfix &ge; 2.6, and all
+versions of Postfix &ge; 2.10 can disable support for "TLSv1.1" or
+"TLSv1.2". </p>
+
+<p> OpenSSL 1.1.1 introduces support for "TLSv1.3". With Postfix
+&ge; 3.4 (or patch releases &ge; 3.0.14, 3.1.10, 3.2.7 and 3.3.2)
+this can be disabled, if need be, via "!TLSv1.3". </p>
+
+<p> To include a protocol list its name, to exclude it, prefix the name
+with a "!" character. To exclude SSLv2 for opportunistic TLS set
+"<a href="postconf.5.html#smtpd_tls_protocols">smtpd_tls_protocols</a> = !SSLv2". To exclude both "SSLv2" and "SSLv3" set
+"<a href="postconf.5.html#smtpd_tls_protocols">smtpd_tls_protocols</a> = !SSLv2, !SSLv3". Explicitly listing the protocols to
+include, rather than protocols to exclude, is supported, but not
+recommended. The exclusion form more closely matches the underlying
+OpenSSL interface semantics. </p>
+
+<p> Example: </p>
+<pre>
+<a href="postconf.5.html#smtpd_tls_protocols">smtpd_tls_protocols</a> = !SSLv2, !SSLv3
+</pre>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_received_header">smtpd_tls_received_header</a>
+(default: no)</b></DT><DD>
+
+<p> Request that the Postfix SMTP server produces Received: message
+headers that include information about the protocol and cipher used,
+as well as the remote SMTP client CommonName and client certificate issuer
+CommonName. This is disabled by default, as the information may
+be modified in transit through other mail servers. Only information
+that was recorded by the final destination can be trusted. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_req_ccert">smtpd_tls_req_ccert</a>
+(default: no)</b></DT><DD>
+
+<p> With mandatory TLS encryption, require a trusted remote SMTP client
+certificate in order to allow TLS connections to proceed. This
+option implies "<a href="postconf.5.html#smtpd_tls_ask_ccert">smtpd_tls_ask_ccert</a> = yes". </p>
+
+<p> When TLS encryption is optional, this setting is ignored with
+a warning written to the mail log. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_security_level">smtpd_tls_security_level</a>
+(default: empty)</b></DT><DD>
+
+<p> The SMTP TLS security level for the Postfix SMTP server; when
+a non-empty value is specified, this overrides the obsolete parameters
+<a href="postconf.5.html#smtpd_use_tls">smtpd_use_tls</a> and <a href="postconf.5.html#smtpd_enforce_tls">smtpd_enforce_tls</a>. This parameter is ignored with
+"<a href="postconf.5.html#smtpd_tls_wrappermode">smtpd_tls_wrappermode</a> = yes". </p>
+
+<p> Specify one of the following security levels: </p>
+
+<dl>
+
+<dt><b>none</b></dt> <dd> TLS will not be used. </dd>
+
+<dt><b>may</b></dt> <dd> Opportunistic TLS: announce STARTTLS support
+to remote SMTP clients, but do not require that clients use TLS encryption.
+</dd>
+
+<dt><b>encrypt</b></dt> <dd>Mandatory TLS encryption: announce
+STARTTLS support to remote SMTP clients, and require that clients use TLS
+encryption. According to <a href="http://tools.ietf.org/html/rfc2487">RFC 2487</a> this MUST NOT be applied in case
+of a publicly-referenced SMTP server. Instead, this option should
+be used only on dedicated servers. </dd>
+
+</dl>
+
+<p> Note 1: the "fingerprint", "verify" and "secure" levels are not
+supported here.
+The Postfix SMTP server logs a warning and uses "encrypt" instead.
+To verify remote SMTP client certificates, see <a href="TLS_README.html">TLS_README</a> for a discussion
+of the <a href="postconf.5.html#smtpd_tls_ask_ccert">smtpd_tls_ask_ccert</a>, <a href="postconf.5.html#smtpd_tls_req_ccert">smtpd_tls_req_ccert</a>, and <a href="postconf.5.html#permit_tls_clientcerts">permit_tls_clientcerts</a>
+features. </p>
+
+<p> Note 2: The parameter setting "<a href="postconf.5.html#smtpd_tls_security_level">smtpd_tls_security_level</a> =
+encrypt" implies "<a href="postconf.5.html#smtpd_tls_auth_only">smtpd_tls_auth_only</a> = yes".</p>
+
+<p> Note 3: when invoked via "sendmail -bs", Postfix will never
+offer STARTTLS due to insufficient privileges to access the server
+private key. This is intended behavior.</p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_session_cache_database">smtpd_tls_session_cache_database</a>
+(default: empty)</b></DT><DD>
+
+<p> Name of the file containing the optional Postfix SMTP server
+TLS session cache. Specify a database type that supports enumeration,
+such as <b>btree</b> or <b>sdbm</b>; there is no need to support
+concurrent access. The file is created if it does not exist. The <a href="smtpd.8.html">smtpd(8)</a>
+daemon does not use this parameter directly, rather the cache is
+implemented indirectly in the <a href="tlsmgr.8.html">tlsmgr(8)</a> daemon. This means that
+per-smtpd-instance <a href="master.5.html">master.cf</a> overrides of this parameter are not
+effective. Note, that each of the cache databases supported by <a href="tlsmgr.8.html">tlsmgr(8)</a>
+daemon: $<a href="postconf.5.html#smtpd_tls_session_cache_database">smtpd_tls_session_cache_database</a>, $<a href="postconf.5.html#smtp_tls_session_cache_database">smtp_tls_session_cache_database</a>
+(and with Postfix 2.3 and later $<a href="postconf.5.html#lmtp_tls_session_cache_database">lmtp_tls_session_cache_database</a>), needs to be
+stored separately. It is not at this time possible to store multiple
+caches in a single database. </p>
+
+<p> Note: <b>dbm</b> databases are not suitable. TLS
+session objects are too large. </p>
+
+<p> As of version 2.5, Postfix no longer uses root privileges when
+opening this file. The file should now be stored under the Postfix-owned
+<a href="postconf.5.html#data_directory">data_directory</a>. As a migration aid, an attempt to open the file
+under a non-Postfix directory is redirected to the Postfix-owned
+<a href="postconf.5.html#data_directory">data_directory</a>, and a warning is logged. </p>
+
+<p> As of Postfix 2.11 the preferred mechanism for session resumption
+is <a href="http://tools.ietf.org/html/rfc5077">RFC 5077</a> TLS session tickets, which don't require server-side
+storage. Consequently, for Postfix &ge; 2.11 this parameter should
+generally be left empty. TLS session tickets require an OpenSSL
+library (at least version 0.9.8h) that provides full support for
+this TLS extension. See also <a href="postconf.5.html#smtpd_tls_session_cache_timeout">smtpd_tls_session_cache_timeout</a>. </p>
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#smtpd_tls_session_cache_database">smtpd_tls_session_cache_database</a> = <a href="DATABASE_README.html#types">btree</a>:/var/lib/postfix/smtpd_scache
+</pre>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_session_cache_timeout">smtpd_tls_session_cache_timeout</a>
+(default: 3600s)</b></DT><DD>
+
+<p> The expiration time of Postfix SMTP server TLS session cache
+information. A cache cleanup is performed periodically
+every $<a href="postconf.5.html#smtpd_tls_session_cache_timeout">smtpd_tls_session_cache_timeout</a> seconds. As with
+$<a href="postconf.5.html#smtpd_tls_session_cache_database">smtpd_tls_session_cache_database</a>, this parameter is implemented in the
+<a href="tlsmgr.8.html">tlsmgr(8)</a> daemon and therefore per-smtpd-instance <a href="master.5.html">master.cf</a> overrides
+are not possible. </p>
+
+<p> As of Postfix 2.11 this setting cannot exceed 100 days. If set
+&le; 0, session caching is disabled, not just via the database, but
+also via <a href="http://tools.ietf.org/html/rfc5077">RFC 5077</a> TLS session tickets, which don't require server-side
+storage. If set to a positive value less than 2 minutes, the minimum
+value of 2 minutes is used instead. TLS session tickets require
+an OpenSSL library (at least version 0.9.8h) that provides full
+support for this TLS extension. </p>
+
+<p> This feature is available in Postfix 2.2 and later, and updated
+for TLS session ticket support in Postfix 2.11. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_tls_wrappermode">smtpd_tls_wrappermode</a>
+(default: no)</b></DT><DD>
+
+<p> Run the Postfix SMTP server in the non-standard "wrapper" mode,
+instead of using the STARTTLS command. </p>
+
+<p> If you want to support this service, enable a special port in
+<a href="master.5.html">master.cf</a>, and specify "-o <a href="postconf.5.html#smtpd_tls_wrappermode">smtpd_tls_wrappermode</a>=yes" on the SMTP
+server's command line. Port 465 (smtps) was once chosen for this
+purpose. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_upstream_proxy_protocol">smtpd_upstream_proxy_protocol</a>
+(default: empty)</b></DT><DD>
+
+<p> The name of the proxy protocol used by an optional before-smtpd
+proxy agent. When a proxy agent is used, this protocol conveys local
+and remote address and port information. Specify
+"<a href="postconf.5.html#smtpd_upstream_proxy_protocol">smtpd_upstream_proxy_protocol</a> = haproxy" to enable the haproxy
+protocol. </p>
+
+<p> NOTE: To use the nginx proxy with <a href="smtpd.8.html">smtpd(8)</a>, enable the XCLIENT
+protocol with <a href="postconf.5.html#smtpd_authorized_xclient_hosts">smtpd_authorized_xclient_hosts</a>. This supports SASL
+authentication in the proxy agent (Postfix 2.9 and later). <p>
+
+<p> This feature is available in Postfix 2.10 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_upstream_proxy_timeout">smtpd_upstream_proxy_timeout</a>
+(default: 5s)</b></DT><DD>
+
+<p> The time limit for the proxy protocol specified with the
+<a href="postconf.5.html#smtpd_upstream_proxy_protocol">smtpd_upstream_proxy_protocol</a> parameter. </p>
+
+<p> This feature is available in Postfix 2.10 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtpd_use_tls">smtpd_use_tls</a>
+(default: no)</b></DT><DD>
+
+<p> Opportunistic TLS: announce STARTTLS support to remote SMTP clients,
+but do not require that clients use TLS encryption. </p>
+
+<p> Note: when invoked via "<b>sendmail -bs</b>", Postfix will never offer
+STARTTLS due to insufficient privileges to access the server private
+key. This is intended behavior. </p>
+
+<p> This feature is available in Postfix 2.2 and later. With
+Postfix 2.3 and later use <a href="postconf.5.html#smtpd_tls_security_level">smtpd_tls_security_level</a> instead. </p>
+
+
+</DD>
+
+<DT><b><a name="smtputf8_autodetect_classes">smtputf8_autodetect_classes</a>
+(default: sendmail, verify)</b></DT><DD>
+
+<p> Detect that a message requires SMTPUTF8 support for the specified
+mail origin classes. This is a workaround to avoid chicken-and-egg
+problems during the initial SMTPUTF8 roll-out in environments with
+pre-existing mail flows that contain UTF8. Those mail flows should
+not break because Postfix suddenly refuses to deliver such mail
+to down-stream MTAs that don't announce SMTPUTF8 support. </p>
+
+<p> The problem is that Postfix cannot rely solely on the sender's
+declaration that a message requires SMTPUTF8 support, because UTF8
+may be introduced during local processing (for example, the client
+hostname in Postfix's Received: header, adding @$<a href="postconf.5.html#myorigin">myorigin</a> or
+.$<a href="postconf.5.html#mydomain">mydomain</a> to an incomplete address, address rewriting, alias
+expansion, automatic BCC recipients, local forwarding, and changes
+made by header checks or Milter applications). </p>
+
+<p> For now, the default is to enable "SMTPUTF8 required" autodetection
+only for Postfix sendmail command-line submissions and address
+verification probes. This may change once SMTPUTF8 support achieves
+world domination. However, sites that add UTF8 content via local
+processing (see above) should autodetect the need for SMTPUTF8
+support for all email.</p>
+
+<p> Specify one or more of the following: </p>
+
+<dl compact>
+
+<dt> <b> sendmail </b> </dt> <dd> Submission with the Postfix
+<a href="sendmail.1.html">sendmail(1)</a> command. </dd>
+
+<dt> <b> smtpd </b> </dt> <dd> Mail received with the <a href="smtpd.8.html">smtpd(8)</a>
+daemon. </dd>
+
+<dt> <b> qmqpd </b> </dt> <dd> Mail received with the <a href="qmqpd.8.html">qmqpd(8)</a>
+daemon. </dd>
+
+<dt> <b> forward </b> </dt> <dd> Local forwarding or aliasing. When
+a message is received with "SMTPUTF8 required", then the forwarded
+(aliased) message always has "SMTPUTF8 required". </dd>
+
+<dt> <b> bounce </b> </dt> <dd> Submission by the <a href="bounce.8.html">bounce(8)</a> daemon.
+When a message is received with "SMTPUTF8 required", then the
+delivery status notification always has "SMTPUTF8 required". </dd>
+
+<dt> <b> notify </b> </dt> <dd> Postmaster notification from the
+<a href="smtp.8.html">smtp(8)</a> or <a href="smtpd.8.html">smtpd(8)</a> daemon. </dd>
+
+<dt> <b> verify </b> </dt> <dd> Address verification probe from the
+<a href="verify.8.html">verify(8)</a> daemon. </dd>
+
+<dt> <b> all </b> </dt> <dd> Enable SMTPUTF8 autodetection for all
+mail. </dd>
+
+</dl>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="smtputf8_enable">smtputf8_enable</a>
+(default: yes)</b></DT><DD>
+
+<p> Enable preliminary SMTPUTF8 support for the protocols described
+in <a href="http://tools.ietf.org/html/rfc6531">RFC 6531</a>..6533. This requires that Postfix is built to support
+these protocols. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="soft_bounce">soft_bounce</a>
+(default: no)</b></DT><DD>
+
+<p>
+Safety net to keep mail queued that would otherwise be returned to
+the sender. This parameter disables locally-generated bounces,
+changes the handling of negative responses from remote servers,
+content filters or plugins,
+and prevents the Postfix SMTP server from rejecting mail permanently
+by changing 5xx reply codes into 4xx. However, <a href="postconf.5.html#soft_bounce">soft_bounce</a> is no
+cure for address rewriting mistakes or mail routing mistakes.
+</p>
+
+<p>
+Note: "<a href="postconf.5.html#soft_bounce">soft_bounce</a> = yes" is in some cases implemented by modifying
+server responses. Therefore, the response that Postfix logs may
+differ from the response that Postfix actually sends or receives.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#soft_bounce">soft_bounce</a> = yes
+</pre>
+
+
+</DD>
+
+<DT><b><a name="stale_lock_time">stale_lock_time</a>
+(default: 500s)</b></DT><DD>
+
+<p>
+The time after which a stale exclusive mailbox lockfile is removed.
+This is used for delivery to file or mailbox.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="stress">stress</a>
+(default: empty)</b></DT><DD>
+
+<p> This feature is documented in the <a href="STRESS_README.html">STRESS_README</a> document. </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="strict_7bit_headers">strict_7bit_headers</a>
+(default: no)</b></DT><DD>
+
+<p>
+Reject mail with 8-bit text in message headers. This blocks mail
+from poorly written applications.
+</p>
+
+<p>
+This feature should not be enabled on a general purpose mail server,
+because it is likely to reject legitimate email.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="strict_8bitmime">strict_8bitmime</a>
+(default: no)</b></DT><DD>
+
+<p>
+Enable both <a href="postconf.5.html#strict_7bit_headers">strict_7bit_headers</a> and <a href="postconf.5.html#strict_8bitmime_body">strict_8bitmime_body</a>.
+</p>
+
+<p>
+This feature should not be enabled on a general purpose mail server,
+because it is likely to reject legitimate email.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="strict_8bitmime_body">strict_8bitmime_body</a>
+(default: no)</b></DT><DD>
+
+<p>
+Reject 8-bit message body text without 8-bit MIME content encoding
+information. This blocks mail from poorly written applications.
+</p>
+
+<p>
+Unfortunately, this also rejects majordomo approval requests when
+the included request contains valid 8-bit MIME mail, and it rejects
+bounces from mailers that do not MIME encapsulate 8-bit content
+(for example, bounces from qmail or from old versions of Postfix).
+</p>
+
+<p>
+This feature should not be enabled on a general purpose mail server,
+because it is likely to reject legitimate email.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="strict_mailbox_ownership">strict_mailbox_ownership</a>
+(default: yes)</b></DT><DD>
+
+<p> Defer delivery when a mailbox file is not owned by its recipient.
+The default setting is not backwards compatible. </p>
+
+<p> This feature is available in Postfix 2.5.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="strict_mime_encoding_domain">strict_mime_encoding_domain</a>
+(default: no)</b></DT><DD>
+
+<p>
+Reject mail with invalid Content-Transfer-Encoding: information
+for the message/* or multipart/* MIME content types. This blocks
+mail from poorly written software.
+</p>
+
+<p>
+This feature should not be enabled on a general purpose mail server,
+because it will reject mail after a single violation.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="strict_rfc821_envelopes">strict_rfc821_envelopes</a>
+(default: no)</b></DT><DD>
+
+<p>
+Require that addresses received in SMTP MAIL FROM and RCPT TO
+commands are enclosed with &lt;&gt;, and that those addresses do
+not contain <a href="http://tools.ietf.org/html/rfc822">RFC 822</a> style comments or phrases. This stops mail
+from poorly written software.
+</p>
+
+<p>
+By default, the Postfix SMTP server accepts <a href="http://tools.ietf.org/html/rfc822">RFC 822</a> syntax in MAIL
+FROM and RCPT TO addresses.
+</p>
+
+
+</DD>
+
+<DT><b><a name="strict_smtputf8">strict_smtputf8</a>
+(default: no)</b></DT><DD>
+
+<p> Enable stricter enforcement of the SMTPUTF8 protocol. The Postfix
+SMTP server accepts UTF8 sender or recipient addresses only when
+the client requests an SMTPUTF8 mail transaction. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="sun_mailtool_compatibility">sun_mailtool_compatibility</a>
+(default: no)</b></DT><DD>
+
+<p>
+Obsolete SUN mailtool compatibility feature. Instead, use
+"<a href="postconf.5.html#mailbox_delivery_lock">mailbox_delivery_lock</a> = dotlock".
+</p>
+
+
+</DD>
+
+<DT><b><a name="swap_bangpath">swap_bangpath</a>
+(default: yes)</b></DT><DD>
+
+<p>
+Enable the rewriting of "site!user" into "user@site". This is
+necessary if your machine is connected to UUCP networks. It is
+enabled by default.
+</p>
+
+<p> Note: with Postfix version 2.2, message header address rewriting
+happens only when one of the following conditions is true: </p>
+
+<ul>
+
+<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,
+
+<li> The message is received from a network client that matches
+$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,
+
+<li> The message is received from the network, and the
+<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.
+
+</ul>
+
+<p> To get the behavior before Postfix version 2.2, specify
+"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all". </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#swap_bangpath">swap_bangpath</a> = no
+</pre>
+
+
+</DD>
+
+<DT><b><a name="syslog_facility">syslog_facility</a>
+(default: mail)</b></DT><DD>
+
+<p>
+The syslog facility of Postfix logging. Specify a facility as
+defined in syslog.conf(5). The default facility is "mail".
+</p>
+
+<p>
+Warning: a non-default <a href="postconf.5.html#syslog_facility">syslog_facility</a> setting takes effect only
+after a Postfix process has completed initialization. Errors during
+process initialization will be logged with the default facility.
+Examples are errors while parsing the command line arguments, and
+errors while accessing the Postfix <a href="postconf.5.html">main.cf</a> configuration file.
+</p>
+
+
+</DD>
+
+<DT><b><a name="syslog_name">syslog_name</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+A prefix that is prepended to the process name in syslog
+records, so that, for example, "smtpd" becomes "prefix/smtpd".
+</p>
+
+<p>
+Warning: a non-default <a href="postconf.5.html#syslog_name">syslog_name</a> setting takes effect only after
+a Postfix process has completed initialization. Errors during
+process initialization will be logged with the default name. Examples
+are errors while parsing the command line arguments, and errors
+while accessing the Postfix <a href="postconf.5.html">main.cf</a> configuration file.
+</p>
+
+
+</DD>
+
+<DT><b><a name="tcp_windowsize">tcp_windowsize</a>
+(default: 0)</b></DT><DD>
+
+<p> An optional workaround for routers that break TCP window scaling.
+Specify a value &gt; 0 and &lt; 65536 to enable this feature. With
+Postfix TCP servers (<a href="smtpd.8.html">smtpd(8)</a>, <a href="qmqpd.8.html">qmqpd(8)</a>), this feature is implemented
+by the Postfix <a href="master.8.html">master(8)</a> daemon. </p>
+
+<p> To change this parameter without stopping Postfix, you need to
+first terminate all Postfix TCP servers: </p>
+
+<blockquote>
+<pre>
+# postconf -e <a href="postconf.5.html#master_service_disable">master_service_disable</a>=inet
+# postfix reload
+</pre>
+</blockquote>
+
+<p> This immediately terminates all processes that accept network
+connections. Next, you enable Postfix TCP servers with the updated
+<a href="postconf.5.html#tcp_windowsize">tcp_windowsize</a> setting: </p>
+
+<blockquote>
+<pre>
+# postconf -e <a href="postconf.5.html#tcp_windowsize">tcp_windowsize</a>=65535 <a href="postconf.5.html#master_service_disable">master_service_disable</a>=
+# postfix reload
+</pre>
+</blockquote>
+
+<p> If you skip these steps with a running Postfix system, then the
+<a href="postconf.5.html#tcp_windowsize">tcp_windowsize</a> change will work only for Postfix TCP clients (<a href="smtp.8.html">smtp(8)</a>,
+<a href="lmtp.8.html">lmtp(8)</a>). </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_append_default_CA">tls_append_default_CA</a>
+(default: no)</b></DT><DD>
+
+<p> Append the system-supplied default Certification Authority
+certificates to the ones specified with *_tls_CApath or *_tls_CAfile.
+The default is "no"; this prevents Postfix from trusting third-party
+certificates and giving them relay permission with
+<a href="postconf.5.html#permit_tls_all_clientcerts">permit_tls_all_clientcerts</a>. </p>
+
+<p> This feature is available in Postfix 2.4.15, 2.5.11, 2.6.8,
+2.7.2 and later versions. Specify "<a href="postconf.5.html#tls_append_default_CA">tls_append_default_CA</a> = yes" for
+backwards compatibility, to avoid breaking certificate verification
+with sites that don't use <a href="postconf.5.html#permit_tls_all_clientcerts">permit_tls_all_clientcerts</a>. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_daemon_random_bytes">tls_daemon_random_bytes</a>
+(default: 32)</b></DT><DD>
+
+<p> The number of pseudo-random bytes that an <a href="smtp.8.html">smtp(8)</a> or <a href="smtpd.8.html">smtpd(8)</a>
+process requests from the <a href="tlsmgr.8.html">tlsmgr(8)</a> server in order to seed its
+internal pseudo random number generator (PRNG). The default of 32
+bytes (equivalent to 256 bits) is sufficient to generate a 128bit
+(or 168bit) session key. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_dane_digest_agility">tls_dane_digest_agility</a>
+(default: on)</b></DT><DD>
+
+<p> Configure <a href="http://tools.ietf.org/html/rfc7671">RFC7671</a> DANE TLSA digest algorithm agility.
+Do not change this setting from its default value. </p>
+
+<p> See Section 8 of <a href="http://tools.ietf.org/html/rfc7671">RFC7671</a> for correct key rotation procedures. </p>
+
+<p> This feature is available in Postfix 2.11 through 3.1. Postfix
+3.2 and later ignore this configuration parameter and behave as
+though it were set to "on". </p>
+
+
+</DD>
+
+<DT><b><a name="tls_dane_digests">tls_dane_digests</a>
+(default: sha512 sha256)</b></DT><DD>
+
+<p> DANE TLSA (<a href="http://tools.ietf.org/html/rfc6698">RFC 6698</a>, <a href="http://tools.ietf.org/html/rfc7671">RFC 7671</a>, <a href="http://tools.ietf.org/html/rfc7672">RFC 7672</a>) resource-record "matching
+type" digest algorithms in descending preference order. All the
+specified algorithms must be supported by the underlying OpenSSL
+library, otherwise the Postfix SMTP client will not support DANE
+TLSA security. </p>
+
+<p> Specify a list of digest names separated by commas and/or
+whitespace. Each digest name may be followed by an optional
+"=&lt;number&gt;" suffix. For example, "sha512" may instead be specified
+as "sha512=2" and "sha256" may instead be specified as "sha256=1".
+The optional number must match the <a
+href="https://www.iana.org/assignments/dane-parameters/dane-parameters.xhtml#matching-types"
+>IANA</a> assigned TLSA matching type number the algorithm in question.
+Postfix will check this constraint for the algorithms it knows about.
+Additional matching type algorithms registered with IANA can be added
+with explicit numbers provided they are supported by OpenSSL. </p>
+
+<p> Invalid list elements are logged with a warning and disable DANE
+support. TLSA RRs that specify digests not included in the list are
+ignored with a warning. </p>
+
+<p> Note: It is unwise to omit sha256 from the digest list. This
+digest algorithm is the only mandatory to implement digest algorithm
+in <a href="http://tools.ietf.org/html/rfc6698">RFC 6698</a>, and many servers are expected publish TLSA records
+with just sha256 digests. Unless one of the standard digests is
+seriously compromised and servers have had ample time to update their
+TLSA records you should not omit any standard digests, just arrange
+them in order from strongest to weakest. </p>
+
+<p> This feature is available in Postfix 2.11 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_dane_trust_anchor_digest_enable">tls_dane_trust_anchor_digest_enable</a>
+(default: yes)</b></DT><DD>
+
+<p> Enable support for <a href="http://tools.ietf.org/html/rfc6698">RFC 6698</a> (DANE TLSA) DNS records that contain
+digests of trust-anchors with certificate usage "2". Do not change
+this setting from its default value. </p>
+
+<p> This feature is available in Postfix 2.11 through 3.1. It has
+been withdrawn in Postfix 3.2, as trust-anchor TLSA records are now
+widely used and have proved sufficiently reliable. Postfix 3.2 and
+later ignore this configuration parameter and behaves as though it
+were set to "yes". </p>
+
+
+</DD>
+
+<DT><b><a name="tls_disable_workarounds">tls_disable_workarounds</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> List or bit-mask of OpenSSL bug work-arounds to disable. </p>
+
+<p> The OpenSSL toolkit includes a set of work-arounds for buggy SSL/TLS
+implementations. Applications, such as Postfix, that want to maximize
+interoperability ask the OpenSSL library to enable the full set of
+recommended work-arounds. </p>
+
+<p> From time to time, it is discovered that a work-around creates a
+security issue, and should no longer be used. If upgrading OpenSSL
+to a fixed version is not an option or an upgrade is not available
+in a timely manner, or in closed environments where no buggy clients
+or servers exist, it may be appropriate to disable some or all of the
+OpenSSL interoperability work-arounds. This parameter specifies which
+bug work-arounds to disable. </p>
+
+<p> If the value of the parameter is a hexadecimal long integer starting
+with "0x", the bug work-arounds corresponding to the bits specified in
+its value are removed from the <b>SSL_OP_ALL</b> work-around bit-mask
+(see openssl/ssl.h and SSL_CTX_set_options(3)). You can specify more
+bits than are present in SSL_OP_ALL, excess bits are ignored. Specifying
+0xFFFFFFFF disables all bug-workarounds on a 32-bit system. This should
+also be sufficient on 64-bit systems, until OpenSSL abandons support
+for 32-bit systems and starts using the high 32 bits of a 64-bit
+bug-workaround mask. </p>
+
+<p> Otherwise, the parameter is a white-space or comma separated list
+of specific named bug work-arounds chosen from the list below. It
+is possible that your OpenSSL version includes new bug work-arounds
+added after your Postfix source code was last updated, in that case
+you can only disable one of these via the hexadecimal syntax above. </p>
+
+<dl>
+
+<dt><b>CRYPTOPRO_TLSEXT_BUG</b></dt> <dd>New with GOST support in
+OpenSSL 1.0.0.</dd>
+
+<dt><b>DONT_INSERT_EMPTY_FRAGMENTS</b></dt> <dd>See
+SSL_CTX_set_options(3)</dd>
+
+<dt><b>LEGACY_SERVER_CONNECT</b></dt> <dd>See SSL_CTX_set_options(3)</dd>
+
+<dt><b>MICROSOFT_BIG_SSLV3_BUFFER</b></dt> <dd>See
+SSL_CTX_set_options(3)</dd>
+
+<dt><b>MICROSOFT_SESS_ID_BUG</b></dt> <dd>See SSL_CTX_set_options(3)</dd>
+
+<dt><b>MSIE_SSLV2_RSA_PADDING</b></dt> <dd> also aliased as
+<b>CVE-2005-2969</b>. Postfix 2.8 disables this work-around by
+default with OpenSSL versions that may predate the fix. Fixed in
+OpenSSL 0.9.7h and OpenSSL 0.9.8a.</dd>
+
+<dt><b>NETSCAPE_CHALLENGE_BUG</b></dt> <dd>See SSL_CTX_set_options(3)</dd>
+
+<dt><b>NETSCAPE_REUSE_CIPHER_CHANGE_BUG</b></dt> <dd> also aliased
+as <b>CVE-2010-4180</b>. Postfix 2.8 disables this work-around by
+default with OpenSSL versions that may predate the fix. Fixed in
+OpenSSL 0.9.8q and OpenSSL 1.0.0c.</dd>
+
+<dt><b>SSLEAY_080_CLIENT_DH_BUG</b></dt> <dd>See
+SSL_CTX_set_options(3)</dd>
+
+<dt><b>SSLREF2_REUSE_CERT_TYPE_BUG</b></dt> <dd>See
+SSL_CTX_set_options(3)</dd>
+
+<dt><b>TLS_BLOCK_PADDING_BUG</b></dt> <dd>See SSL_CTX_set_options(3)</dd>
+
+<dt><b>TLS_D5_BUG</b></dt> <dd>See SSL_CTX_set_options(3)</dd>
+
+<dt><b>TLS_ROLLBACK_BUG</b></dt> <dd>See SSL_CTX_set_options(3).
+This is disabled in OpenSSL 0.9.7 and later. Nobody should still
+be using 0.9.6! </dd>
+
+<dt><b>TLSEXT_PADDING</b></dt><dd>Postfix &ge; 3.4. See SSL_CTX_set_options(3).</dd>
+
+</dl>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_eecdh_auto_curves">tls_eecdh_auto_curves</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The prioritized list of elliptic curves supported by the Postfix
+SMTP client and server. These curves are used by the Postfix SMTP
+server when "<a href="postconf.5.html#smtpd_tls_eecdh_grade">smtpd_tls_eecdh_grade</a> = auto". The selected curves
+must be implemented by OpenSSL and be standardized for use in TLS
+(<a href="http://tools.ietf.org/html/rfc4492">RFC 4492</a> or its imminent successor). It is unwise to list only
+"bleeding-edge" curves supported by a small subset of clients. The
+default list is suitable for most users. </p>
+
+<p> Postfix skips curve names that are unknown to OpenSSL, or that
+are known but not yet implemented. This makes it possible to
+"anticipate" support for curves that should be used once they become
+available. In particular, in some OpenSSL versions, the new <a href="http://tools.ietf.org/html/rfc8031">RFC</a>
+<a href="http://tools.ietf.org/html/rfc8031">8031</a> curves "X25519" and "X448" may be known by name, but ECDH
+support for either or both may be missing. These curves may appear
+in the default value of this parameter, even though they'll only
+be usable with later versions of OpenSSL. </p>
+
+<p> This feature is available in Postfix 3.2 and later, when it is
+compiled and linked with OpenSSL 1.0.2 or later on platforms where
+EC algorithms have not been disabled by the vendor. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_eecdh_strong_curve">tls_eecdh_strong_curve</a>
+(default: prime256v1)</b></DT><DD>
+
+<p> The elliptic curve used by the Postfix SMTP server for sensibly
+strong
+ephemeral ECDH key exchange. This curve is used by the Postfix SMTP
+server when "<a href="postconf.5.html#smtpd_tls_eecdh_grade">smtpd_tls_eecdh_grade</a> = strong". The phrase "sensibly
+strong" means approximately 128-bit security based on best known
+attacks. The selected curve must be implemented by OpenSSL (as
+reported by ecparam(1) with the "-list_curves" option) and be one
+of the curves listed in Section 5.1.1 of <a href="http://tools.ietf.org/html/rfc4492">RFC 4492</a>. You should not
+generally change this setting. Remote SMTP client implementations
+must support this curve for EECDH key exchange to take place. It
+is unwise to choose an "bleeding-edge" curve supported by only a
+small subset of clients. </p>
+
+<p> The default "strong" curve is rated in NSA <a
+href="http://www.nsa.gov/ia/programs/suiteb_cryptography/">Suite
+B</a> for information classified up to SECRET. </p>
+
+<p> Note: elliptic curve names are poorly standardized; different
+standards groups are assigning different names to the same underlying
+curves. The curve with the X9.62 name "prime256v1" is also known
+under the SECG name "secp256r1", but OpenSSL does not recognize the
+latter name. </p>
+
+<p> If you want to take maximal advantage of ciphers that offer <a
+href="FORWARD_SECRECY_README.html#dfn_fs">forward secrecy</a> see
+the <a href="FORWARD_SECRECY_README.html#quick-start">Getting
+started</a> section of <a
+href="FORWARD_SECRECY_README.html">FORWARD_SECRECY_README</a>. The
+full document conveniently presents all information about Postfix
+"perfect" forward secrecy support in one place: what forward secrecy
+is, how to tweak settings, and what you can expect to see when
+Postfix uses ciphers with forward secrecy. </p>
+
+<p> This feature is available in Postfix 2.6 and later, when it is
+compiled and linked with OpenSSL 1.0.0 or later on platforms where
+EC algorithms have not been disabled by the vendor. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_eecdh_ultra_curve">tls_eecdh_ultra_curve</a>
+(default: secp384r1)</b></DT><DD>
+
+<p> The elliptic curve used by the Postfix SMTP server for maximally
+strong
+ephemeral ECDH key exchange. This curve is used by the Postfix SMTP
+server when "<a href="postconf.5.html#smtpd_tls_eecdh_grade">smtpd_tls_eecdh_grade</a> = ultra". The phrase "maximally
+strong" means approximately 192-bit security based on best known attacks.
+This additional strength comes at a significant computational cost, most
+users should instead set "<a href="postconf.5.html#smtpd_tls_eecdh_grade">smtpd_tls_eecdh_grade</a> = strong". The selected
+curve must be implemented by OpenSSL (as reported by ecparam(1) with the
+"-list_curves" option) and be one of the curves listed in Section 5.1.1
+of <a href="http://tools.ietf.org/html/rfc4492">RFC 4492</a>. You should not generally change this setting. </p>
+
+<p> This default "ultra" curve is rated in NSA <a
+href="http://www.nsa.gov/ia/programs/suiteb_cryptography/">Suite
+B</a> for information classified up to TOP SECRET. </p>
+
+<p> If you want to take maximal advantage of ciphers that offer <a
+href="FORWARD_SECRECY_README.html#dfn_fs">forward secrecy</a> see
+the <a href="FORWARD_SECRECY_README.html#quick-start">Getting
+started</a> section of <a
+href="FORWARD_SECRECY_README.html">FORWARD_SECRECY_README</a>. The
+full document conveniently presents all information about Postfix
+"perfect" forward secrecy support in one place: what forward secrecy
+is, how to tweak settings, and what you can expect to see when
+Postfix uses ciphers with forward secrecy. </p>
+
+<p> This feature is available in Postfix 2.6 and later, when it is
+compiled and linked with OpenSSL 1.0.0 or later on platforms where
+EC algorithms have not been disabled by the vendor. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_export_cipherlist">tls_export_cipherlist</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The OpenSSL cipherlist for "export" or higher grade ciphers. This
+defines the meaning of the "export" setting in <a href="postconf.5.html#smtpd_tls_ciphers">smtpd_tls_ciphers</a>,
+<a href="postconf.5.html#smtpd_tls_mandatory_ciphers">smtpd_tls_mandatory_ciphers</a>, <a href="postconf.5.html#smtp_tls_ciphers">smtp_tls_ciphers</a>, <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a>,
+<a href="postconf.5.html#lmtp_tls_ciphers">lmtp_tls_ciphers</a>, and <a href="postconf.5.html#lmtp_tls_mandatory_ciphers">lmtp_tls_mandatory_ciphers</a>. With Postfix
+releases before the middle of 2015 this is the default cipherlist
+for the opportunistic ("may") TLS client security level and also
+the default cipherlist for the SMTP server. You are strongly
+encouraged to not change this setting. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_fast_shutdown_enable">tls_fast_shutdown_enable</a>
+(default: yes)</b></DT><DD>
+
+<p> A workaround for implementations that hang Postfix while shuting
+down a TLS session, until Postfix times out. With this enabled,
+Postfix will not wait for the remote TLS peer to respond to a TLS
+'close' notification. This behavior is recommended for TLSv1.0 and
+later. </p>
+
+<p> This feature was introduced with Postfix 3.4.6, 3.3.5, 3.2.10,
+and 3.1.13. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_high_cipherlist">tls_high_cipherlist</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The OpenSSL cipherlist for "high" grade ciphers. This defines
+the meaning of the "high" setting in <a href="postconf.5.html#smtpd_tls_ciphers">smtpd_tls_ciphers</a>,
+<a href="postconf.5.html#smtpd_tls_mandatory_ciphers">smtpd_tls_mandatory_ciphers</a>, <a href="postconf.5.html#smtp_tls_ciphers">smtp_tls_ciphers</a>, <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a>,
+<a href="postconf.5.html#lmtp_tls_ciphers">lmtp_tls_ciphers</a>, and <a href="postconf.5.html#lmtp_tls_mandatory_ciphers">lmtp_tls_mandatory_ciphers</a>. You are strongly
+encouraged to not change this setting. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_legacy_public_key_fingerprints">tls_legacy_public_key_fingerprints</a>
+(default: no)</b></DT><DD>
+
+<p> A temporary migration aid for sites that use certificate
+<i>public-key</i> fingerprints with Postfix 2.9.0..2.9.5, which use
+an incorrect algorithm. This parameter has no effect on the certificate
+fingerprint support that is available since Postfix 2.2. </p>
+
+<p> Specify "<a href="postconf.5.html#tls_legacy_public_key_fingerprint">tls_legacy_public_key_fingerprints</a> = yes" temporarily,
+pending a migration from configuration files with incorrect Postfix
+2.9.0..2.9.5 certificate public-key finger prints, to the correct
+fingerprints used by Postfix 2.9.6 and later. To compute the correct
+certificate public-key fingerprints, see <a href="TLS_README.html">TLS_README</a>. </p>
+
+<p> This feature is available in Postfix 2.9.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_low_cipherlist">tls_low_cipherlist</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The OpenSSL cipherlist for "low" or higher grade ciphers. This defines
+the meaning of the "low" setting in <a href="postconf.5.html#smtpd_tls_ciphers">smtpd_tls_ciphers</a>,
+<a href="postconf.5.html#smtpd_tls_mandatory_ciphers">smtpd_tls_mandatory_ciphers</a>, <a href="postconf.5.html#smtp_tls_ciphers">smtp_tls_ciphers</a>, <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a>,
+<a href="postconf.5.html#lmtp_tls_ciphers">lmtp_tls_ciphers</a>, and <a href="postconf.5.html#lmtp_tls_mandatory_ciphers">lmtp_tls_mandatory_ciphers</a>. You are strongly
+encouraged to not change this setting. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_medium_cipherlist">tls_medium_cipherlist</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The OpenSSL cipherlist for "medium" or higher grade ciphers. This
+defines the meaning of the "medium" setting in <a href="postconf.5.html#smtpd_tls_ciphers">smtpd_tls_ciphers</a>,
+<a href="postconf.5.html#smtpd_tls_mandatory_ciphers">smtpd_tls_mandatory_ciphers</a>, <a href="postconf.5.html#smtp_tls_ciphers">smtp_tls_ciphers</a>, <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a>,
+<a href="postconf.5.html#lmtp_tls_ciphers">lmtp_tls_ciphers</a>, and <a href="postconf.5.html#lmtp_tls_mandatory_ciphers">lmtp_tls_mandatory_ciphers</a>. This is the
+default cipherlist for mandatory TLS encryption in the TLS client
+(with anonymous ciphers disabled when verifying server certificates).
+This is the default cipherlist for opportunistic TLS with Postfix
+releases after the middle of 2015. You are strongly encouraged to
+not change this setting. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_null_cipherlist">tls_null_cipherlist</a>
+(default: eNULL:!aNULL)</b></DT><DD>
+
+<p> The OpenSSL cipherlist for "NULL" grade ciphers that provide
+authentication without encryption. This defines the meaning of the "null"
+setting in smtpd_mandatory_tls_ciphers, <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> and
+<a href="postconf.5.html#lmtp_tls_mandatory_ciphers">lmtp_tls_mandatory_ciphers</a>. You are strongly encouraged to not
+change this setting. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_preempt_cipherlist">tls_preempt_cipherlist</a>
+(default: no)</b></DT><DD>
+
+<p> With SSLv3 and later, use the Postfix SMTP server's cipher
+preference order instead of the remote client's cipher preference
+order. </p>
+
+<p> By default, the OpenSSL server selects the client's most preferred
+cipher that the server supports. With SSLv3 and later, the server may
+choose its own most preferred cipher that is supported (offered) by
+the client. Setting "<a href="postconf.5.html#tls_preempt_cipherlist">tls_preempt_cipherlist</a> = yes" enables server cipher
+preferences. </p>
+
+<p> While server cipher selection may in some cases lead to a more secure
+or performant cipher choice, there is some risk of interoperability
+issues. In the past, some SSL clients have listed lower priority ciphers
+that they did not implement correctly. If the server chooses a cipher
+that the client prefers less, it may select a cipher whose client
+implementation is flawed. Most notably Windows 2003 Microsoft
+Exchange servers have flawed implementations of DES-CBC3-SHA, which
+OpenSSL considers stronger than RC4-SHA. Enabling server cipher-suite
+selection may create interoperability issues with Windows 2003
+Microsoft Exchange clients. </p>
+
+<p> This feature is available in Postfix 2.8 and later, in combination
+with OpenSSL 0.9.7 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_random_bytes">tls_random_bytes</a>
+(default: 32)</b></DT><DD>
+
+<p> The number of bytes that <a href="tlsmgr.8.html">tlsmgr(8)</a> reads from $<a href="postconf.5.html#tls_random_source">tls_random_source</a>
+when (re)seeding the in-memory pseudo random number generator (PRNG)
+pool. The default of 32 bytes (256 bits) is good enough for 128bit
+symmetric keys. If using EGD or a device file, a maximum of 255
+bytes is read. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_random_exchange_name">tls_random_exchange_name</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> Name of the pseudo random number generator (PRNG) state file
+that is maintained by <a href="tlsmgr.8.html">tlsmgr(8)</a>. The file is created when it does
+not exist, and its length is fixed at 1024 bytes. </p>
+
+<p> As of version 2.5, Postfix no longer uses root privileges when
+opening this file, and the default file location was changed from
+${<a href="postconf.5.html#config_directory">config_directory</a>}/prng_exch to ${<a href="postconf.5.html#data_directory">data_directory</a>}/prng_exch. As
+a migration aid, an attempt to open the file under a non-Postfix
+directory is redirected to the Postfix-owned <a href="postconf.5.html#data_directory">data_directory</a>, and a
+warning is logged. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_random_prng_update_period">tls_random_prng_update_period</a>
+(default: 3600s)</b></DT><DD>
+
+<p> The time between attempts by <a href="tlsmgr.8.html">tlsmgr(8)</a> to save the state of
+the pseudo random number generator (PRNG) to the file specified
+with $<a href="postconf.5.html#tls_random_exchange_name">tls_random_exchange_name</a>. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_random_reseed_period">tls_random_reseed_period</a>
+(default: 3600s)</b></DT><DD>
+
+<p> The maximal time between attempts by <a href="tlsmgr.8.html">tlsmgr(8)</a> to re-seed the
+in-memory pseudo random number generator (PRNG) pool from external
+sources. The actual time between re-seeding attempts is calculated
+using the PRNG, and is between 0 and the time specified. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_random_source">tls_random_source</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p> The external entropy source for the in-memory <a href="tlsmgr.8.html">tlsmgr(8)</a> pseudo
+random number generator (PRNG) pool. Be sure to specify a non-blocking
+source. If this source is not a regular file, the entropy source
+type must be prepended: egd:/path/to/egd_socket for a source with
+EGD compatible socket interface, or dev:/path/to/device for a
+device file. </p>
+
+<p> Note: on OpenBSD systems specify /dev/arandom when /dev/urandom
+gives timeout errors. </p>
+
+<p> This feature is available in Postfix 2.2 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_server_sni_maps">tls_server_sni_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional lookup tables that map names received from remote SMTP
+clients via the TLS Server Name Indication (SNI) extension to the
+appropriate keys and certificate chains. This parameter is implemented
+in the Postfix TLS library, and applies to both <a href="smtpd.8.html">smtpd(8)</a> and the SMTP
+server mode of <a href="tlsproxy.8.html">tlsproxy(8)</a>. </p>
+
+<p> The lookup key is either the verbatim SNI domain name or an
+ancestor domain prefixed with a leading dot. For internationalized
+domains, the lookup key must be in IDNA 2008 A-label form (as
+required in the TLS SNI extension). </p>
+
+<p> When this parameter is non-empty, the Postfix SMTP server enables
+SNI extension processing, and logs SNI values that are invalid or
+don't match an entry in the the specified tables. When an entry
+does match, the SNI name is logged as part of the connection summary
+at log levels 1 and higher. </p>
+
+<p> Note that the SNI lookup tables should also have entries for
+the domains that correspond to the Postfix SMTP server's default
+certificate(s). This ensures that the remote SMTP client's TLS SNI
+extension gets a positive response when it specifies one of the
+Postfix SMTP server's <a href="ADDRESS_CLASS_README.html#default_domain_class">default domains</a>, and ensures that the Postfix
+SMTP server will not log an SNI name mismatch for such a domain.
+The Postfix SMTP server's default certificates are then only used
+when the client sends no SNI or when it sends SNI with a domain
+that the server knows no certificate(s) for. </p>
+
+<p> The mapping from an SNI domain name to a certificate chain is
+typically indirect. In the input source files for "cdb", "hash",
+"btree" or other tables that are converted to on-disk indexed files
+via <a href="postmap.1.html">postmap(1)</a>, the value specified for each key is a list of
+filenames. When <a href="postmap.1.html">postmap(1)</a> is used with the <b>-F</b> option, the
+generated table stores for each lookup key the base64-encoded
+contents of the associated files. When querying tables via <b>postmap
+-Fq</b>, the table value is decoded from base64, yielding the original
+file content, plus a new line. </p>
+
+<p> With "regexp", "pcre", "inline", "texthash", "static" and similar
+tables that are interpreted at run-time, and don't have a separate
+source format, the table value is again a list files, that are read-in
+when the table is opened. </p>
+
+<p> Thus, for example: </p>
+
+<blockquote>
+<pre>
+$ postmap -Fq "" <a href="DATABASE_README.html#types">static</a>:/etc/postfix/chain.pem | openssl dgst -sha1
+(stdin)= da39a3ee5e6b4b0d3255bfef95601890afd80709
+</pre>
+</blockquote>
+
+<p> produces the same output as: </p>
+
+<blockquote>
+<pre>
+$ (cat /etc/postfix/chain.pem; echo) | openssl dgst -sha1
+(stdin)= da39a3ee5e6b4b0d3255bfef95601890afd80709
+</pre>
+</blockquote>
+
+<p> With tables whose content is managed outside of Postfix, such
+as LDAP, MySQL, PostgreSQL, socketmap and tcp, the value must be a
+concatenation of the desired PEM keys and certificate chains, that
+is then further encoded to yield a single-line base64 string.
+Creation of such tables and secure storage are outside the
+responsibility of Postfix. With "socketmap" and "tcp" the data
+would be transmitted in the clear. With LDAP and SQL, you should
+generally use TLS to protect the sensitive data in transit. </p>
+
+<p> Typically there is only private key and its chain of certificates
+starting with the "leaf" certificate corresponding to that key, and
+continuing with the appropriate intermediate issuer CA certificates,
+with each certificate ideally followed by its issuer. Servers
+that have keys and certificates for more than one algorithm (e.g.
+both an RSA key and an ECDSA key, or even RSA, ECDSA and Ed25519)
+can use multiple chains concatenated together, with the key always
+listed before the corresponding certificates. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_session_ticket_cipher">tls_session_ticket_cipher</a>
+(default: Postfix &ge; 3.0: aes-256-cbc, Postfix &lt; 3.0: aes-128-cbc)</b></DT><DD>
+
+<p> Algorithm used to encrypt <a href="http://tools.ietf.org/html/rfc5077">RFC5077</a> TLS session tickets. This
+algorithm must use CBC mode, have a 128-bit block size, and must
+have a key length between 128 and 256 bits. The default is
+aes-256-cbc. Overriding the default to choose a different algorithm
+is discouraged. </p>
+
+<p> Setting this parameter empty disables session ticket support
+in the Postfix SMTP server. Another way to disable session ticket
+support is via the <a href="postconf.5.html#tls_ssl_options">tls_ssl_options</a> parameter. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_ssl_options">tls_ssl_options</a>
+(default: empty)</b></DT><DD>
+
+<p> List or bit-mask of OpenSSL options to enable. </p>
+
+<p> The OpenSSL toolkit provides a set of options that applications
+can enable to tune the OpenSSL behavior. Some of these work around
+bugs in other implementations and are on by default. You can use
+the <a href="postconf.5.html#tls_disable_workarounds">tls_disable_workarounds</a> parameter to selectively disable some
+or all of the bug work-arounds, making OpenSSL more strict at the
+cost of non-interoperability with SSL clients or servers that exhibit
+the bugs. </p>
+
+<p> Other options are off by default, and typically enable or disable
+features rather than bug work-arounds. These may be turned on (with
+care) via the <a href="postconf.5.html#tls_ssl_options">tls_ssl_options</a> parameter. The value is a white-space
+or comma separated list of named options chosen from the list below.
+The names are not case-sensitive, you can use lower-case if you
+prefer. The upper case values below match the corresponding macro
+name in the ssl.h header file with the SSL_OP_ prefix removed. It
+is possible that your OpenSSL version includes new options added
+after your Postfix source code was last updated, in that case you
+can only enable one of these via the hexadecimal syntax below. </p>
+
+<p> You should only enable features via the hexadecimal mask when
+the need to control the feature is critical (to deal with a new
+vulnerability or a serious interoperability problem). Postfix DOES
+NOT promise backwards compatible behavior with respect to the mask
+bits. A feature enabled via the mask in one release may be enabled
+by other means in a later release, and the mask bit will then be
+ignored. Therefore, use of the hexadecimal mask is only a temporary
+measure until a new Postfix or OpenSSL release provides a better
+solution. </p>
+
+<p> If the value of the parameter is a hexadecimal long integer
+starting with "0x", the options corresponding to the bits specified
+in its value are enabled (see openssl/ssl.h and SSL_CTX_set_options(3)).
+You can only enable options not already controlled by other Postfix
+settings. For example, you cannot disable protocols or enable
+server cipher preference. Do not attempt to turn all features by
+specifying 0xFFFFFFFF, this is unlikely to be a good idea. Some
+bug work-arounds are also valid here, allowing them to be re-enabled
+if/when they're no longer enabled by default. The supported values
+include: </p>
+
+<dl>
+
+<dt><b>ENABLE_MIDDLEBOX_COMPAT</b></dt> <dd>Postfix &ge; 3.4. See
+SSL_CTX_set_options(3).</dd>
+
+<dt><b>LEGACY_SERVER_CONNECT</b></dt> <dd>See SSL_CTX_set_options(3).</dd>
+
+<dt><b>NO_TICKET</b></dt> <dd>Enabled by default when needed in
+fully-patched Postfix &ge; 2.7. Not needed at all for Postfix &ge;
+2.11, unless for some reason you do not want to support TLS session
+resumption. Best not set explicitly. See SSL_CTX_set_options(3).</dd>
+
+<dt><b>NO_COMPRESSION</b></dt> <dd>Disable SSL compression even if
+supported by the OpenSSL library. Compression is CPU-intensive,
+and compression before encryption does not always improve security. </dd>
+
+<dt><b>NO_RENEGOTIATION</b></dt> <dd>Postfix &ge; 3.4. This can
+reduce opportunities for a potential CPU exhaustion attack. See
+SSL_CTX_set_options(3).</dd>
+
+<dt><b>NO_SESSION_RESUMPTION_ON_RENEGOTIATION</b></dt> <dd>Postfix
+&ge; 3.4. See SSL_CTX_set_options(3).</dd>
+
+<dt><b>PRIORITIZE_CHACHA</b></dt> <dd>Postfix &ge; 3.4. See SSL_CTX_set_options(3).</dd>
+
+</dl>
+
+<p> This feature is available in Postfix 2.11 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tls_wildcard_matches_multiple_labels">tls_wildcard_matches_multiple_labels</a>
+(default: yes)</b></DT><DD>
+
+<p> Match multiple DNS labels with "*" in wildcard certificates.
+</p>
+
+<p> Some mail service providers prepend the customer domain name
+to a base domain for which they have a wildcard TLS certificate.
+For example, the MX records for example.com hosted by example.net
+may be: </p>
+
+<blockquote>
+<pre>
+example.com. IN MX 0 example.com.mx1.example.net.
+example.com. IN MX 0 example.com.mx2.example.net.
+</pre>
+</blockquote>
+
+<p> and the TLS certificate may be for "*.example.net". The "*"
+then corresponds with multiple labels in the mail server domain
+name. While multi-label wildcards are not widely supported, and
+are not blessed by any standard, there is little to be gained by
+disallowing their use in this context. </p>
+
+<p> Notes: <p>
+
+<ul>
+
+<li> <p> In a certificate name, the "*" is special only when it is
+used as the first label. </p>
+
+<li> <p> While Postfix (2.11 or later) can match "*" with multiple
+domain name labels, other implementations likely will not. </p>
+
+<li> <p> Earlier Postfix implementations behave as if
+"<a href="postconf.5.html#tls_wildcard_matches_multiple_labels">tls_wildcard_matches_multiple_labels</a> = no". </p>
+
+</ul>
+
+<p> This feature is available in Postfix 2.11 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsmgr_service_name">tlsmgr_service_name</a>
+(default: tlsmgr)</b></DT><DD>
+
+<p> The name of the <a href="tlsmgr.8.html">tlsmgr(8)</a> service entry in <a href="master.5.html">master.cf</a>. This
+service maintains TLS session caches and other information in support
+of TLS. </p>
+
+<p> This feature is available in Postfix 2.11 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_CAfile">tlsproxy_client_CAfile</a>
+(default: $<a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a>)</b></DT><DD>
+
+<p> A file containing CA certificates of root CAs trusted to sign
+either remote TLS server certificates or intermediate CA certificates.
+See <a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a> for further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_CApath">tlsproxy_client_CApath</a>
+(default: $<a href="postconf.5.html#smtp_tls_CApath">smtp_tls_CApath</a>)</b></DT><DD>
+
+<p> Directory with PEM format Certification Authority certificates
+that the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> client uses to verify a remote TLS
+server certificate. See <a href="postconf.5.html#smtp_tls_CApath">smtp_tls_CApath</a> for further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_cert_file">tlsproxy_client_cert_file</a>
+(default: $<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>)</b></DT><DD>
+
+<p> File with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> client RSA certificate in PEM
+format. See <a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> for further details. The preferred way
+to configure tlsproxy client keys and certificates is via the
+"<a href="postconf.5.html#tlsproxy_client_chain_files">tlsproxy_client_chain_files</a>" parameter. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_chain_files">tlsproxy_client_chain_files</a>
+(default: $<a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a>)</b></DT><DD>
+
+<p> Files with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> client keys and certificate
+chains in PEM format. See <a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a> for further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_dcert_file">tlsproxy_client_dcert_file</a>
+(default: $<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a>)</b></DT><DD>
+
+<p> File with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> client DSA certificate in PEM
+format. See <a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a> for further details. DSA is obsolete and
+should not be used. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_dkey_file">tlsproxy_client_dkey_file</a>
+(default: $<a href="postconf.5.html#smtp_tls_dkey_file">smtp_tls_dkey_file</a>)</b></DT><DD>
+
+<p> File with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> client DSA private key in PEM
+format. See <a href="postconf.5.html#smtp_tls_dkey_file">smtp_tls_dkey_file</a> for further details. DSA is obsolete and
+should not be used. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_eccert_file">tlsproxy_client_eccert_file</a>
+(default: $<a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a>)</b></DT><DD>
+
+<p> File with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> client ECDSA certificate in PEM
+format. See <a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a> for further details. The preferred way
+to configure tlsproxy client keys and certificates is via the
+"<a href="postconf.5.html#tlsproxy_client_chain_files">tlsproxy_client_chain_files</a>" parameter. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_eckey_file">tlsproxy_client_eckey_file</a>
+(default: $<a href="postconf.5.html#smtp_tls_eckey_file">smtp_tls_eckey_file</a>)</b></DT><DD>
+
+<p> File with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> client ECDSA private key in PEM
+format. See <a href="postconf.5.html#smtp_tls_eckey_file">smtp_tls_eckey_file</a> for further details. The preferred way
+to configure tlsproxy client keys and certificates is via the
+"<a href="postconf.5.html#tlsproxy_client_chain_files">tlsproxy_client_chain_files</a>" parameter. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_enforce_tls">tlsproxy_client_enforce_tls</a>
+(default: $<a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a>)</b></DT><DD>
+
+<p> Enforcement mode: require that SMTP servers use TLS encryption.
+See <a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a> for further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_fingerprint_digest">tlsproxy_client_fingerprint_digest</a>
+(default: $<a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a>)</b></DT><DD>
+
+<p> The message digest algorithm used to construct remote TLS server
+certificate fingerprints. See <a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a> for
+further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_key_file">tlsproxy_client_key_file</a>
+(default: $<a href="postconf.5.html#smtp_tls_key_file">smtp_tls_key_file</a>)</b></DT><DD>
+
+<p> File with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> client RSA private key in PEM
+format. See <a href="postconf.5.html#smtp_tls_key_file">smtp_tls_key_file</a> for further details. The preferred way to
+configure tlsproxy client keys and certificates is via the
+"<a href="postconf.5.html#tlsproxy_client_chain_files">tlsproxy_client_chain_files</a>" parameter. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_loglevel">tlsproxy_client_loglevel</a>
+(default: $<a href="postconf.5.html#smtp_tls_loglevel">smtp_tls_loglevel</a>)</b></DT><DD>
+
+<p> Enable additional Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> client logging of TLS
+activity. See <a href="postconf.5.html#smtp_tls_loglevel">smtp_tls_loglevel</a> for further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_loglevel_parameter">tlsproxy_client_loglevel_parameter</a>
+(default: <a href="postconf.5.html#smtp_tls_loglevel">smtp_tls_loglevel</a>)</b></DT><DD>
+
+<p> The name of the parameter that provides the <a href="postconf.5.html#tlsproxy_client_loglevel">tlsproxy_client_loglevel</a>
+value. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_per_site">tlsproxy_client_per_site</a>
+(default: $<a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a>)</b></DT><DD>
+
+<p> Optional lookup tables with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> client TLS
+usage policy by next-hop destination and by remote TLS server
+hostname. See <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> for further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_policy_maps">tlsproxy_client_policy_maps</a>
+(default: $<a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>)</b></DT><DD>
+
+<p> Optional lookup tables with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> client TLS
+security policy by next-hop destination. See <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>
+for further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_scert_verifydepth">tlsproxy_client_scert_verifydepth</a>
+(default: $<a href="postconf.5.html#smtp_tls_scert_verifydepth">smtp_tls_scert_verifydepth</a>)</b></DT><DD>
+
+<p> The verification depth for remote TLS server certificates.
+See <a href="postconf.5.html#smtp_tls_scert_verifydepth">smtp_tls_scert_verifydepth</a> for further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_security_level">tlsproxy_client_security_level</a>
+(default: $<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a>)</b></DT><DD>
+
+<p> The default TLS security level for the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a>
+client. See <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> for further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_client_use_tls">tlsproxy_client_use_tls</a>
+(default: $<a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a>)</b></DT><DD>
+
+<p> Opportunistic mode: use TLS when a remote server announces TLS
+support. See <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a> for further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_enforce_tls">tlsproxy_enforce_tls</a>
+(default: $<a href="postconf.5.html#smtpd_enforce_tls">smtpd_enforce_tls</a>)</b></DT><DD>
+
+<p> Mandatory TLS: announce STARTTLS support to remote SMTP clients, and
+require that clients use TLS encryption. See <a href="postconf.5.html#smtpd_enforce_tls">smtpd_enforce_tls</a> for
+further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_service_name">tlsproxy_service_name</a>
+(default: tlsproxy)</b></DT><DD>
+
+<p> The name of the <a href="tlsproxy.8.html">tlsproxy(8)</a> service entry in <a href="master.5.html">master.cf</a>. This
+service performs plaintext &lt;=&gt; TLS ciphertext conversion. <p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_CAfile">tlsproxy_tls_CAfile</a>
+(default: $<a href="postconf.5.html#smtpd_tls_CAfile">smtpd_tls_CAfile</a>)</b></DT><DD>
+
+<p> A file containing (PEM format) CA certificates of root CAs
+trusted to sign either remote SMTP client certificates or intermediate
+CA certificates. See <a href="postconf.5.html#smtpd_tls_CAfile">smtpd_tls_CAfile</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_CApath">tlsproxy_tls_CApath</a>
+(default: $<a href="postconf.5.html#smtpd_tls_CApath">smtpd_tls_CApath</a>)</b></DT><DD>
+
+<p> A directory containing (PEM format) CA certificates of root CAs
+trusted to sign either remote SMTP client certificates or intermediate
+CA certificates. See <a href="postconf.5.html#smtpd_tls_CApath">smtpd_tls_CApath</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_always_issue_session_ids">tlsproxy_tls_always_issue_session_ids</a>
+(default: $<a href="postconf.5.html#smtpd_tls_always_issue_session_ids">smtpd_tls_always_issue_session_ids</a>)</b></DT><DD>
+
+<p> Force the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server to issue a TLS session id,
+even when TLS session caching is turned off. See
+<a href="postconf.5.html#smtpd_tls_always_issue_session_ids">smtpd_tls_always_issue_session_ids</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_ask_ccert">tlsproxy_tls_ask_ccert</a>
+(default: $<a href="postconf.5.html#smtpd_tls_ask_ccert">smtpd_tls_ask_ccert</a>)</b></DT><DD>
+
+<p> Ask a remote SMTP client for a client certificate. See
+<a href="postconf.5.html#smtpd_tls_ask_ccert">smtpd_tls_ask_ccert</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_ccert_verifydepth">tlsproxy_tls_ccert_verifydepth</a>
+(default: $<a href="postconf.5.html#smtpd_tls_ccert_verifydepth">smtpd_tls_ccert_verifydepth</a>)</b></DT><DD>
+
+<p> The verification depth for remote SMTP client certificates. A
+depth of 1 is sufficient if the issuing CA is listed in a local CA
+file. See <a href="postconf.5.html#smtpd_tls_ccert_verifydepth">smtpd_tls_ccert_verifydepth</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_cert_file">tlsproxy_tls_cert_file</a>
+(default: $<a href="postconf.5.html#smtpd_tls_cert_file">smtpd_tls_cert_file</a>)</b></DT><DD>
+
+<p> File with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server RSA certificate in PEM
+format. This file may also contain the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server
+private RSA key. See <a href="postconf.5.html#smtpd_tls_cert_file">smtpd_tls_cert_file</a> for further details. With
+Postfix &ge; 3.4 the preferred way to configure tlsproxy server keys and
+certificates is via the "<a href="postconf.5.html#tlsproxy_tls_chain_files">tlsproxy_tls_chain_files</a>" parameter. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_chain_files">tlsproxy_tls_chain_files</a>
+(default: $<a href="postconf.5.html#smtpd_tls_chain_files">smtpd_tls_chain_files</a>)</b></DT><DD>
+
+<p> Files with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server keys and certificate
+chains in PEM format. See <a href="postconf.5.html#smtpd_tls_chain_files">smtpd_tls_chain_files</a> for further details. </p>
+
+<p> This feature is available in Postfix 3.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_ciphers">tlsproxy_tls_ciphers</a>
+(default: $<a href="postconf.5.html#smtpd_tls_ciphers">smtpd_tls_ciphers</a>)</b></DT><DD>
+
+<p> The minimum TLS cipher grade that the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server
+will use with opportunistic TLS encryption. See <a href="postconf.5.html#smtpd_tls_ciphers">smtpd_tls_ciphers</a>
+for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_dcert_file">tlsproxy_tls_dcert_file</a>
+(default: $<a href="postconf.5.html#smtpd_tls_dcert_file">smtpd_tls_dcert_file</a>)</b></DT><DD>
+
+<p> File with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server DSA certificate in PEM
+format. This file may also contain the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server
+private DSA key. DSA is obsolete and should not be used. See
+<a href="postconf.5.html#smtpd_tls_dcert_file">smtpd_tls_dcert_file</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_dh1024_param_file">tlsproxy_tls_dh1024_param_file</a>
+(default: $<a href="postconf.5.html#smtpd_tls_dh1024_param_file">smtpd_tls_dh1024_param_file</a>)</b></DT><DD>
+
+<p> File with DH parameters that the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server
+should use with non-export EDH ciphers. See <a href="postconf.5.html#smtpd_tls_dh1024_param_file">smtpd_tls_dh1024_param_file</a>
+for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_dh512_param_file">tlsproxy_tls_dh512_param_file</a>
+(default: $<a href="postconf.5.html#smtpd_tls_dh512_param_file">smtpd_tls_dh512_param_file</a>)</b></DT><DD>
+
+<p> File with DH parameters that the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server
+should use with export-grade EDH ciphers. See <a href="postconf.5.html#smtpd_tls_dh512_param_file">smtpd_tls_dh512_param_file</a>
+for further details. The default SMTP server cipher grade is
+"medium" with Postfix releases after the middle of 2015, and as a
+result export-grade cipher suites are by default not used. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_dkey_file">tlsproxy_tls_dkey_file</a>
+(default: $<a href="postconf.5.html#smtpd_tls_dkey_file">smtpd_tls_dkey_file</a>)</b></DT><DD>
+
+<p> File with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server DSA private key in PEM
+format. This file may be combined with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server
+DSA certificate file specified with $<a href="postconf.5.html#smtpd_tls_dcert_file">smtpd_tls_dcert_file</a>. DSA is
+obsolete and should not be used. See <a href="postconf.5.html#smtpd_tls_dkey_file">smtpd_tls_dkey_file</a> for further
+details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_eccert_file">tlsproxy_tls_eccert_file</a>
+(default: $<a href="postconf.5.html#smtpd_tls_eccert_file">smtpd_tls_eccert_file</a>)</b></DT><DD>
+
+<p> File with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server ECDSA certificate in PEM
+format. This file may also contain the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server
+private ECDSA key. See <a href="postconf.5.html#smtpd_tls_eccert_file">smtpd_tls_eccert_file</a> for further details. With
+Postfix &ge; 3.4 the preferred way to configure tlsproxy server keys and
+certificates is via the "<a href="postconf.5.html#tlsproxy_tls_chain_files">tlsproxy_tls_chain_files</a>" parameter. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_eckey_file">tlsproxy_tls_eckey_file</a>
+(default: $<a href="postconf.5.html#smtpd_tls_eckey_file">smtpd_tls_eckey_file</a>)</b></DT><DD>
+
+<p> File with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server ECDSA private key in PEM
+format. This file may be combined with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server
+ECDSA certificate file specified with $<a href="postconf.5.html#smtpd_tls_eccert_file">smtpd_tls_eccert_file</a>. See
+<a href="postconf.5.html#smtpd_tls_eckey_file">smtpd_tls_eckey_file</a> for further details. With Postfix &ge; 3.4 the
+preferred way to configure tlsproxy server keys and certificates is via
+the "<a href="postconf.5.html#tlsproxy_tls_chain_files">tlsproxy_tls_chain_files</a>" parameter. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_eecdh_grade">tlsproxy_tls_eecdh_grade</a>
+(default: $<a href="postconf.5.html#smtpd_tls_eecdh_grade">smtpd_tls_eecdh_grade</a>)</b></DT><DD>
+
+<p> The Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server security grade for ephemeral
+elliptic-curve Diffie-Hellman (EECDH) key exchange. See
+<a href="postconf.5.html#smtpd_tls_eecdh_grade">smtpd_tls_eecdh_grade</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_exclude_ciphers">tlsproxy_tls_exclude_ciphers</a>
+(default: $<a href="postconf.5.html#smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a>)</b></DT><DD>
+
+<p> List of ciphers or cipher types to exclude from the <a href="tlsproxy.8.html">tlsproxy(8)</a>
+server cipher list at all TLS security levels. See
+<a href="postconf.5.html#smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_fingerprint_digest">tlsproxy_tls_fingerprint_digest</a>
+(default: $<a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a>)</b></DT><DD>
+
+<p> The message digest algorithm to construct remote SMTP
+client-certificate
+fingerprints. See <a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> for further details.
+</p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_key_file">tlsproxy_tls_key_file</a>
+(default: $<a href="postconf.5.html#smtpd_tls_key_file">smtpd_tls_key_file</a>)</b></DT><DD>
+
+<p> File with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server RSA private key in PEM
+format. This file may be combined with the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server
+RSA certificate file specified with $<a href="postconf.5.html#smtpd_tls_cert_file">smtpd_tls_cert_file</a>. See
+<a href="postconf.5.html#smtpd_tls_key_file">smtpd_tls_key_file</a> for further details. With Postfix &ge; 3.4 the
+preferred way to configure tlsproxy server keys and certificates is via
+the "<a href="postconf.5.html#tlsproxy_tls_chain_files">tlsproxy_tls_chain_files</a>" parameter. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_loglevel">tlsproxy_tls_loglevel</a>
+(default: $<a href="postconf.5.html#smtpd_tls_loglevel">smtpd_tls_loglevel</a>)</b></DT><DD>
+
+<p> Enable additional Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server logging of TLS
+activity. Each logging level also includes the information that
+is logged at a lower logging level. See <a href="postconf.5.html#smtpd_tls_loglevel">smtpd_tls_loglevel</a> for
+further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_mandatory_ciphers">tlsproxy_tls_mandatory_ciphers</a>
+(default: $<a href="postconf.5.html#smtpd_tls_mandatory_ciphers">smtpd_tls_mandatory_ciphers</a>)</b></DT><DD>
+
+<p> The minimum TLS cipher grade that the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server
+will use with mandatory TLS encryption. See <a href="postconf.5.html#smtpd_tls_mandatory_ciphers">smtpd_tls_mandatory_ciphers</a>
+for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_mandatory_exclude_ciphers">tlsproxy_tls_mandatory_exclude_ciphers</a>
+(default: $<a href="postconf.5.html#smtpd_tls_mandatory_exclude_ciphers">smtpd_tls_mandatory_exclude_ciphers</a>)</b></DT><DD>
+
+<p> Additional list of ciphers or cipher types to exclude from the
+<a href="tlsproxy.8.html">tlsproxy(8)</a> server cipher list at mandatory TLS security levels.
+See <a href="postconf.5.html#smtpd_tls_mandatory_exclude_ciphers">smtpd_tls_mandatory_exclude_ciphers</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_mandatory_protocols">tlsproxy_tls_mandatory_protocols</a>
+(default: $<a href="postconf.5.html#smtpd_tls_mandatory_protocols">smtpd_tls_mandatory_protocols</a>)</b></DT><DD>
+
+<p> The SSL/TLS protocols accepted by the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server
+with mandatory TLS encryption. If the list is empty, the server
+supports all available SSL/TLS protocol versions. See
+<a href="postconf.5.html#smtpd_tls_mandatory_protocols">smtpd_tls_mandatory_protocols</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_protocols">tlsproxy_tls_protocols</a>
+(default: $<a href="postconf.5.html#smtpd_tls_protocols">smtpd_tls_protocols</a>)</b></DT><DD>
+
+<p> List of TLS protocols that the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server will
+exclude or include with opportunistic TLS encryption. See
+<a href="postconf.5.html#smtpd_tls_protocols">smtpd_tls_protocols</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_req_ccert">tlsproxy_tls_req_ccert</a>
+(default: $<a href="postconf.5.html#smtpd_tls_req_ccert">smtpd_tls_req_ccert</a>)</b></DT><DD>
+
+<p> With mandatory TLS encryption, require a trusted remote SMTP
+client certificate in order to allow TLS connections to proceed.
+See <a href="postconf.5.html#smtpd_tls_req_ccert">smtpd_tls_req_ccert</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_security_level">tlsproxy_tls_security_level</a>
+(default: $<a href="postconf.5.html#smtpd_tls_security_level">smtpd_tls_security_level</a>)</b></DT><DD>
+
+<p> The SMTP TLS security level for the Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server;
+when a non-empty value is specified, this overrides the obsolete
+parameters <a href="postconf.5.html#smtpd_use_tls">smtpd_use_tls</a> and <a href="postconf.5.html#smtpd_enforce_tls">smtpd_enforce_tls</a>. See
+<a href="postconf.5.html#smtpd_tls_security_level">smtpd_tls_security_level</a> for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_tls_session_cache_timeout">tlsproxy_tls_session_cache_timeout</a>
+(default: $<a href="postconf.5.html#smtpd_tls_session_cache_timeout">smtpd_tls_session_cache_timeout</a>)</b></DT><DD>
+
+<p> Obsolete expiration time of Postfix <a href="tlsproxy.8.html">tlsproxy(8)</a> server TLS session
+cache information. Since the cache is shared with <a href="smtpd.8.html">smtpd(8)</a> and managed
+by <a href="tlsmgr.8.html">tlsmgr(8)</a>, there is only one expiration time for the SMTP server cache
+shared by all three services, namely <a href="postconf.5.html#smtpd_tls_session_cache_timeout">smtpd_tls_session_cache_timeout</a>. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_use_tls">tlsproxy_use_tls</a>
+(default: $<a href="postconf.5.html#smtpd_use_tls">smtpd_use_tls</a>)</b></DT><DD>
+
+<p> Opportunistic TLS: announce STARTTLS support to remote SMTP clients,
+but do not require that clients use TLS encryption. See <a href="postconf.5.html#smtpd_use_tls">smtpd_use_tls</a>
+for further details. </p>
+
+<p> This feature is available in Postfix 2.8 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="tlsproxy_watchdog_timeout">tlsproxy_watchdog_timeout</a>
+(default: 10s)</b></DT><DD>
+
+<p> How much time a <a href="tlsproxy.8.html">tlsproxy(8)</a> process may take to process local
+or remote I/O before it is terminated by a built-in watchdog timer.
+This is a safety mechanism that prevents <a href="tlsproxy.8.html">tlsproxy(8)</a> from becoming
+non-responsive due to a bug in Postfix itself or in system software.
+To avoid false alarms and unnecessary cache corruption this limit
+cannot be set under 10s. </p>
+
+<p> Specify a non-zero time value (an integral value plus an optional
+one-letter suffix that specifies the time unit). Time units: s
+(seconds), m (minutes), h (hours), d (days), w (weeks). </p>
+
+<p> This feature is available in Postfix 2.8 and later </p>
+
+
+</DD>
+
+<DT><b><a name="trace_service_name">trace_service_name</a>
+(default: trace)</b></DT><DD>
+
+<p>
+The name of the trace service. This service is implemented by the
+<a href="bounce.8.html">bounce(8)</a> daemon and maintains a record
+of mail deliveries and produces a mail delivery report when verbose
+delivery is requested with "<b>sendmail -v</b>".
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="transport_delivery_slot_cost">transport_delivery_slot_cost</a>
+(default: $<a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a>)</b></DT><DD>
+
+<p> A transport-specific override for the <a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a>
+parameter value, where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of
+the message delivery transport. </p>
+
+<p> Note: <a href="postconf.5.html#transport_delivery_slot_cost"><i>transport</i>_delivery_slot_cost</a> parameters will not
+show up in "postconf" command output before Postfix version 2.9.
+This limitation applies to many parameters whose name is a combination
+of a <a href="master.5.html">master.cf</a> service name and a built-in suffix (in this case:
+"_delivery_slot_cost"). </p>
+
+
+</DD>
+
+<DT><b><a name="transport_delivery_slot_discount">transport_delivery_slot_discount</a>
+(default: $<a href="postconf.5.html#default_delivery_slot_discount">default_delivery_slot_discount</a>)</b></DT><DD>
+
+<p> A transport-specific override for the <a href="postconf.5.html#default_delivery_slot_discount">default_delivery_slot_discount</a>
+parameter value, where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of
+the message delivery transport. </p>
+
+<p> Note: <a href="postconf.5.html#transport_delivery_slot_discount"><i>transport</i>_delivery_slot_discount</a> parameters will
+not show up in "postconf" command output before Postfix version
+2.9. This limitation applies to many parameters whose name is a
+combination of a <a href="master.5.html">master.cf</a> service name and a built-in suffix (in
+this case: "_delivery_slot_discount"). </p>
+
+
+</DD>
+
+<DT><b><a name="transport_delivery_slot_loan">transport_delivery_slot_loan</a>
+(default: $<a href="postconf.5.html#default_delivery_slot_loan">default_delivery_slot_loan</a>)</b></DT><DD>
+
+<p> A transport-specific override for the <a href="postconf.5.html#default_delivery_slot_loan">default_delivery_slot_loan</a>
+parameter value, where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of
+the message delivery transport. </p>
+
+<p> Note: <a href="postconf.5.html#transport_delivery_slot_loan"><i>transport</i>_delivery_slot_loan</a> parameters will not
+show up in "postconf" command output before Postfix version 2.9.
+This limitation applies to many parameters whose name is a combination
+of a <a href="master.5.html">master.cf</a> service name and a built-in suffix (in this case:
+"_delivery_slot_loan"). </p>
+
+
+</DD>
+
+<DT><b><a name="transport_destination_concurrency_failed_cohort_limit">transport_destination_concurrency_failed_cohort_limit</a>
+(default: $<a href="postconf.5.html#default_destination_concurrency_failed_cohort_limit">default_destination_concurrency_failed_cohort_limit</a>)</b></DT><DD>
+
+<p> A transport-specific override for the
+<a href="postconf.5.html#default_destination_concurrency_failed_cohort_limit">default_destination_concurrency_failed_cohort_limit</a> parameter value,
+where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of the message delivery
+transport. </p>
+
+<p> Note: some <a href="postconf.5.html#transport_destination_concurrency_failed_cohort_limit"><i>transport</i>_destination_concurrency_failed_cohort_limit</a>
+parameters will not show up in "postconf" command output before
+Postfix version 2.9. This limitation applies to many parameters
+whose name is a combination of a <a href="master.5.html">master.cf</a> service name and a
+built-in suffix (in this case:
+"_destination_concurrency_failed_cohort_limit"). </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="transport_destination_concurrency_limit">transport_destination_concurrency_limit</a>
+(default: $<a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a>)</b></DT><DD>
+
+<p> A transport-specific override for the
+<a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a> parameter value, where
+<i>transport</i> is the <a href="master.5.html">master.cf</a> name of the message delivery
+transport. </p>
+
+<p> Note: some <a href="postconf.5.html#transport_destination_concurrency_limit"><i>transport</i>_destination_concurrency_limit</a>
+parameters will not show up in "postconf" command output before
+Postfix version 2.9. This limitation applies to many parameters
+whose name is a combination of a <a href="master.5.html">master.cf</a> service name and a
+built-in suffix (in this case: "_destination_concurrency_limit").
+</p>
+
+
+</DD>
+
+<DT><b><a name="transport_destination_concurrency_negative_feedback">transport_destination_concurrency_negative_feedback</a>
+(default: $<a href="postconf.5.html#default_destination_concurrency_negative_feedback">default_destination_concurrency_negative_feedback</a>)</b></DT><DD>
+
+<p> A transport-specific override for the
+<a href="postconf.5.html#default_destination_concurrency_negative_feedback">default_destination_concurrency_negative_feedback</a> parameter value,
+where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of the message delivery
+transport. </p>
+
+<p> Note: some <a href="postconf.5.html#transport_destination_concurrency_negative_feedback"><i>transport</i>_destination_concurrency_negative_feedback</a>
+parameters will not show up in "postconf" command output before
+Postfix version 2.9. This limitation applies to many parameters
+whose name is a combination of a <a href="master.5.html">master.cf</a> service name and a
+built-in suffix (in this case:
+"_destination_concurrency_negative_feedback"). </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="transport_destination_concurrency_positive_feedback">transport_destination_concurrency_positive_feedback</a>
+(default: $<a href="postconf.5.html#default_destination_concurrency_positive_feedback">default_destination_concurrency_positive_feedback</a>)</b></DT><DD>
+
+<p> A transport-specific override for the
+<a href="postconf.5.html#default_destination_concurrency_positive_feedback">default_destination_concurrency_positive_feedback</a> parameter value,
+where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of the message delivery
+transport. </p>
+
+<p> Note: some <a href="postconf.5.html#transport_destination_concurrency_positive_feedback"><i>transport</i>_destination_concurrency_positive_feedback</a>
+parameters will not show up in "postconf" command output before
+Postfix version 2.9. This limitation applies to many parameters
+whose name is a combination of a <a href="master.5.html">master.cf</a> service name and a
+built-in suffix (in this case:
+"_destination_concurrency_positive_feedback"). </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="transport_destination_rate_delay">transport_destination_rate_delay</a>
+(default: $<a href="postconf.5.html#default_destination_rate_delay">default_destination_rate_delay</a>)</b></DT><DD>
+
+<p> A transport-specific override for the <a href="postconf.5.html#default_destination_rate_delay">default_destination_rate_delay</a>
+parameter value, where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of
+the message delivery transport. </p>
+
+<p> Note: some <a href="postconf.5.html#transport_destination_rate_delay"><i>transport</i>_destination_rate_delay</a> parameters
+will not show up in "postconf" command output before Postfix version
+2.9. This limitation applies to many parameters whose name is a
+combination of a <a href="master.5.html">master.cf</a> service name and a built-in suffix (in
+this case: "_destination_rate_delay"). </p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="transport_destination_recipient_limit">transport_destination_recipient_limit</a>
+(default: $<a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a>)</b></DT><DD>
+
+<p> A transport-specific override for the
+<a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a> parameter value, where
+<i>transport</i> is the <a href="master.5.html">master.cf</a> name of the message delivery
+transport. </p>
+
+<p> Note: some <a href="postconf.5.html#transport_destination_recipient_limit"><i>transport</i>_destination_recipient_limit</a> parameters
+will not show up in "postconf" command output before Postfix version
+2.9. This limitation applies to many parameters whose name is a
+combination of a <a href="master.5.html">master.cf</a> service name and a built-in suffix (in
+this case: "_destination_recipient_limit"). </p>
+
+
+</DD>
+
+<DT><b><a name="transport_extra_recipient_limit">transport_extra_recipient_limit</a>
+(default: $<a href="postconf.5.html#default_extra_recipient_limit">default_extra_recipient_limit</a>)</b></DT><DD>
+
+<p> A transport-specific override for the <a href="postconf.5.html#default_extra_recipient_limit">default_extra_recipient_limit</a>
+parameter value, where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of
+the message delivery transport. </p>
+
+<p> Note: <a href="postconf.5.html#transport_extra_recipient_limit"><i>transport</i>_extra_recipient_limit</a> parameters will
+not show up in "postconf" command output before Postfix version
+2.9. This limitation applies to many parameters whose name is a
+combination of a <a href="master.5.html">master.cf</a> service name and a built-in suffix (in
+this case: "_extra_recipient_limit"). </p>
+
+
+</DD>
+
+<DT><b><a name="transport_initial_destination_concurrency">transport_initial_destination_concurrency</a>
+(default: $<a href="postconf.5.html#initial_destination_concurrency">initial_destination_concurrency</a>)</b></DT><DD>
+
+<p> A transport-specific override for the <a href="postconf.5.html#initial_destination_concurrency">initial_destination_concurrency</a>
+parameter value, where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of
+the message delivery transport. </p>
+
+<p> Note: some <a href="postconf.5.html#transport_initial_destination_concurrency"><i>transport</i>_initial_destination_concurrency</a>
+parameters will not show up in "postconf" command output before
+Postfix version 2.9. This limitation applies to many parameters
+whose name is a combination of a <a href="master.5.html">master.cf</a> service name and a
+built-in suffix (in this case: "_initial_destination_concurrency").
+</p>
+
+<p> This feature is available in Postfix 2.5 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="transport_maps">transport_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional lookup tables with mappings from recipient address to
+(message delivery transport, next-hop destination). See <a href="transport.5.html">transport(5)</a>
+for details.
+</p>
+
+<p>
+Specify zero or more "<a href="DATABASE_README.html">type:table</a>" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found. If you use this
+feature with local files, run "<b>postmap /etc/postfix/transport</b>"
+after making a change. </p>
+
+<p> Pattern matching of domain names is controlled by the presence
+or absence of "<a href="postconf.5.html#transport_maps">transport_maps</a>" in the <a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a>
+parameter value. </p>
+
+<p> For safety reasons, as of Postfix 2.3 this feature does not
+allow $number substitutions in regular expression maps. </p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#transport_maps">transport_maps</a> = <a href="DATABASE_README.html#types">dbm</a>:/etc/postfix/transport
+<a href="postconf.5.html#transport_maps">transport_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/transport
+</pre>
+
+
+</DD>
+
+<DT><b><a name="transport_minimum_delivery_slots">transport_minimum_delivery_slots</a>
+(default: $<a href="postconf.5.html#default_minimum_delivery_slots">default_minimum_delivery_slots</a>)</b></DT><DD>
+
+<p> A transport-specific override for the <a href="postconf.5.html#default_minimum_delivery_slots">default_minimum_delivery_slots</a>
+parameter value, where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of
+the message delivery transport. </p>
+
+<p> Note: <a href="postconf.5.html#transport_minimum_delivery_slots"><i>transport</i>_minimum_delivery_slots</a> parameters will
+not show up in "postconf" command output before Postfix version
+2.9. This limitation applies to many parameters whose name is a
+combination of a <a href="master.5.html">master.cf</a> service name and a built-in suffix (in
+this case: "_minimum_delivery_slots"). </p>
+
+
+</DD>
+
+<DT><b><a name="transport_recipient_limit">transport_recipient_limit</a>
+(default: $<a href="postconf.5.html#default_recipient_limit">default_recipient_limit</a>)</b></DT><DD>
+
+<p> A transport-specific override for the <a href="postconf.5.html#default_recipient_limit">default_recipient_limit</a>
+parameter value, where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of
+the message delivery transport. </p>
+
+<p> Note: some <a href="postconf.5.html#transport_recipient_limit"><i>transport</i>_recipient_limit</a> parameters will not
+show up in "postconf" command output before Postfix version 2.9.
+This limitation applies to many parameters whose name is a combination
+of a <a href="master.5.html">master.cf</a> service name and a built-in suffix (in this case:
+"_recipient_limit"). </p>
+
+
+</DD>
+
+<DT><b><a name="transport_recipient_refill_delay">transport_recipient_refill_delay</a>
+(default: $<a href="postconf.5.html#default_recipient_refill_delay">default_recipient_refill_delay</a>)</b></DT><DD>
+
+<p> A transport-specific override for the <a href="postconf.5.html#default_recipient_refill_delay">default_recipient_refill_delay</a>
+parameter value, where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of
+the message delivery transport. </p>
+
+<p> Note: <a href="postconf.5.html#transport_recipient_refill_delay"><i>transport</i>_recipient_refill_delay</a> parameters will
+not show up in "postconf" command output before Postfix version
+2.9. This limitation applies to many parameters whose name is a
+combination of a <a href="master.5.html">master.cf</a> service name and a built-in suffix (in
+this case: "_recipient_refill_delay"). </p>
+
+<p> This feature is available in Postfix 2.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="transport_recipient_refill_limit">transport_recipient_refill_limit</a>
+(default: $<a href="postconf.5.html#default_recipient_refill_limit">default_recipient_refill_limit</a>)</b></DT><DD>
+
+<p> A transport-specific override for the <a href="postconf.5.html#default_recipient_refill_limit">default_recipient_refill_limit</a>
+parameter value, where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of
+the message delivery transport. </p>
+
+<p> Note: <a href="postconf.5.html#transport_recipient_refill_limit"><i>transport</i>_recipient_refill_limit</a> parameters will
+not show up in "postconf" command output before Postfix version
+2.9. This limitation applies to many parameters whose name is a
+combination of a <a href="master.5.html">master.cf</a> service name and a built-in suffix (in
+this case: "_recipient_refill_limit"). </p>
+
+<p> This feature is available in Postfix 2.4 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="transport_retry_time">transport_retry_time</a>
+(default: 60s)</b></DT><DD>
+
+<p>
+The time between attempts by the Postfix queue manager to contact
+a malfunctioning message delivery transport.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="transport_time_limit">transport_time_limit</a>
+(default: $<a href="postconf.5.html#command_time_limit">command_time_limit</a>)</b></DT><DD>
+
+<p> A transport-specific override for the <a href="postconf.5.html#command_time_limit">command_time_limit</a> parameter
+value, where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of the message
+delivery transport. </p>
+
+<p> Note: <a href="postconf.5.html#transport_time_limit"><i>transport</i>_time_limit</a> parameters will not show up
+in "postconf" command output before Postfix version 2.9. This
+limitation applies to many parameters whose name is a combination
+of a <a href="master.5.html">master.cf</a> service name and a built-in suffix (in this case:
+"_time_limit"). </p>
+
+
+</DD>
+
+<DT><b><a name="transport_transport_rate_delay">transport_transport_rate_delay</a>
+(default: $<a href="postconf.5.html#default_transport_rate_delay">default_transport_rate_delay</a>)</b></DT><DD>
+
+<p> A transport-specific override for the <a href="postconf.5.html#default_transport_rate_delay">default_transport_rate_delay</a>
+parameter value, where the initial <i>transport</i> in the parameter
+name is the <a href="master.5.html">master.cf</a> name of the message delivery transport. </p>
+
+
+</DD>
+
+<DT><b><a name="trigger_timeout">trigger_timeout</a>
+(default: 10s)</b></DT><DD>
+
+<p>
+The time limit for sending a trigger to a Postfix daemon (for
+example, the <a href="pickup.8.html">pickup(8)</a> or <a href="qmgr.8.html">qmgr(8)</a> daemon). This time limit prevents
+programs from getting stuck when the mail system is under heavy
+load.
+</p>
+
+<p>
+Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
+The default time unit is s (seconds).
+</p>
+
+
+</DD>
+
+<DT><b><a name="undisclosed_recipients_header">undisclosed_recipients_header</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+Message header that the Postfix <a href="cleanup.8.html">cleanup(8)</a> server inserts when a
+message contains no To: or Cc: message header. With Postfix 2.8
+and later, the default value is empty. With Postfix 2.4-2.7,
+specify an empty value to disable this feature. </p>
+
+<p> Example: </p>
+
+<pre>
+# Default value before Postfix 2.8.
+# Note: the ":" and ";" are both required.
+<a href="postconf.5.html#undisclosed_recipients_header">undisclosed_recipients_header</a> = To: undisclosed-recipients:;
+</pre>
+
+
+</DD>
+
+<DT><b><a name="unknown_address_reject_code">unknown_address_reject_code</a>
+(default: 450)</b></DT><DD>
+
+<p>
+The numerical response code when the Postfix SMTP server rejects a
+sender or recipient address because its domain is unknown. This
+is one of the possible replies from the restrictions
+<a href="postconf.5.html#reject_unknown_sender_domain">reject_unknown_sender_domain</a> and <a href="postconf.5.html#reject_unknown_recipient_domain">reject_unknown_recipient_domain</a>.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="unknown_address_tempfail_action">unknown_address_tempfail_action</a>
+(default: $<a href="postconf.5.html#reject_tempfail_action">reject_tempfail_action</a>)</b></DT><DD>
+
+<p> The Postfix SMTP server's action when <a href="postconf.5.html#reject_unknown_sender_domain">reject_unknown_sender_domain</a>
+or <a href="postconf.5.html#reject_unknown_recipient_domain">reject_unknown_recipient_domain</a> fail due to a temporary error
+condition. Specify "defer" to defer the remote SMTP client request
+immediately. With the default "<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>" action, the Postfix
+SMTP server continues to look for opportunities to reject mail, and
+defers the client request only if it would otherwise be accepted.
+</p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="unknown_client_reject_code">unknown_client_reject_code</a>
+(default: 450)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code when a client
+without valid address &lt;=&gt; name mapping is rejected by the
+<a href="postconf.5.html#reject_unknown_client_hostname">reject_unknown_client_hostname</a> restriction. The SMTP server always replies
+with 450 when the mapping failed due to a temporary error condition.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="unknown_helo_hostname_tempfail_action">unknown_helo_hostname_tempfail_action</a>
+(default: $<a href="postconf.5.html#reject_tempfail_action">reject_tempfail_action</a>)</b></DT><DD>
+
+<p> The Postfix SMTP server's action when <a href="postconf.5.html#reject_unknown_helo_hostname">reject_unknown_helo_hostname</a>
+fails due to a temporary error condition. Specify "defer" to defer
+the remote SMTP client request immediately. With the default
+"<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>" action, the Postfix SMTP server continues to look
+for opportunities to reject mail, and defers the client request
+only if it would otherwise be accepted. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="unknown_hostname_reject_code">unknown_hostname_reject_code</a>
+(default: 450)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code when the hostname
+specified with the HELO or EHLO command is rejected by the
+<a href="postconf.5.html#reject_unknown_helo_hostname">reject_unknown_helo_hostname</a> restriction.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+
+</DD>
+
+<DT><b><a name="unknown_local_recipient_reject_code">unknown_local_recipient_reject_code</a>
+(default: 550)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code when a recipient
+address is local, and $<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> specifies a list of
+lookup tables that does not match the recipient. A recipient
+address is local when its domain matches $<a href="postconf.5.html#mydestination">mydestination</a>,
+$<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a> or $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>.
+</p>
+
+<p>
+The default setting is 550 (reject mail) but it is safer to initially
+use 450 (try again later) so you have time to find out if your
+<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> settings are OK.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#unknown_local_recipient_reject_code">unknown_local_recipient_reject_code</a> = 450
+</pre>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="unknown_relay_recipient_reject_code">unknown_relay_recipient_reject_code</a>
+(default: 550)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server reply code when a recipient
+address matches $<a href="postconf.5.html#relay_domains">relay_domains</a>, and <a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> specifies
+a list of lookup tables that does not match the recipient address.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="unknown_virtual_alias_reject_code">unknown_virtual_alias_reject_code</a>
+(default: 550)</b></DT><DD>
+
+<p>
+The Postfix SMTP server reply code when a recipient address matches
+$<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, and $<a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> specifies a list
+of lookup tables that does not match the recipient address.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="unknown_virtual_mailbox_reject_code">unknown_virtual_mailbox_reject_code</a>
+(default: 550)</b></DT><DD>
+
+<p>
+The Postfix SMTP server reply code when a recipient address matches
+$<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>, and $<a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a> specifies a list
+of lookup tables that does not match the recipient address.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="unverified_recipient_defer_code">unverified_recipient_defer_code</a>
+(default: 450)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response when a recipient address
+probe fails due to a temporary error condition.
+</p>
+
+<p>
+Unlike elsewhere in Postfix, you can specify 250 in order to
+accept the address anyway.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+<p>
+This feature is available in Postfix 2.6 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="unverified_recipient_reject_code">unverified_recipient_reject_code</a>
+(default: 450)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response when a recipient address
+is rejected by the <a href="postconf.5.html#reject_unverified_recipient">reject_unverified_recipient</a> restriction.
+</p>
+
+<p>
+Unlike elsewhere in Postfix, you can specify 250 in order to
+accept the address anyway.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="unverified_recipient_reject_reason">unverified_recipient_reject_reason</a>
+(default: empty)</b></DT><DD>
+
+<p> The Postfix SMTP server's reply when rejecting mail with
+<a href="postconf.5.html#reject_unverified_recipient">reject_unverified_recipient</a>. Do not include the numeric SMTP reply
+code or the enhanced status code. By default, the response includes
+actual address verification details.
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#unverified_recipient_reject_reason">unverified_recipient_reject_reason</a> = Recipient address lookup failed
+</pre>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="unverified_recipient_tempfail_action">unverified_recipient_tempfail_action</a>
+(default: $<a href="postconf.5.html#reject_tempfail_action">reject_tempfail_action</a>)</b></DT><DD>
+
+<p> The Postfix SMTP server's action when <a href="postconf.5.html#reject_unverified_recipient">reject_unverified_recipient</a>
+fails due to a temporary error condition. Specify "defer" to defer
+the remote SMTP client request immediately. With the default
+"<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>" action, the Postfix SMTP server continues to look
+for opportunities to reject mail, and defers the client request
+only if it would otherwise be accepted. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="unverified_sender_defer_code">unverified_sender_defer_code</a>
+(default: 450)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code when a sender address
+probe fails due to a temporary error condition.
+</p>
+
+<p>
+Unlike elsewhere in Postfix, you can specify 250 in order to
+accept the address anyway.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+<p>
+This feature is available in Postfix 2.6 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="unverified_sender_reject_code">unverified_sender_reject_code</a>
+(default: 450)</b></DT><DD>
+
+<p>
+The numerical Postfix SMTP server response code when a recipient
+address is rejected by the <a href="postconf.5.html#reject_unverified_sender">reject_unverified_sender</a> restriction.
+</p>
+
+<p>
+Unlike elsewhere in Postfix, you can specify 250 in order to
+accept the address anyway.
+</p>
+
+<p>
+Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc5321">RFC 5321</a>.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="unverified_sender_reject_reason">unverified_sender_reject_reason</a>
+(default: empty)</b></DT><DD>
+
+<p> The Postfix SMTP server's reply when rejecting mail with
+<a href="postconf.5.html#reject_unverified_sender">reject_unverified_sender</a>. Do not include the numeric SMTP reply
+code or the enhanced status code. By default, the response includes
+actual address verification details.
+
+<p> Example: </p>
+
+<pre>
+<a href="postconf.5.html#unverified_sender_reject_reason">unverified_sender_reject_reason</a> = Sender address lookup failed
+</pre>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="unverified_sender_tempfail_action">unverified_sender_tempfail_action</a>
+(default: $<a href="postconf.5.html#reject_tempfail_action">reject_tempfail_action</a>)</b></DT><DD>
+
+<p> The Postfix SMTP server's action when <a href="postconf.5.html#reject_unverified_sender">reject_unverified_sender</a>
+fails due to a temporary error condition. Specify "defer" to defer
+the remote SMTP client request immediately. With the default
+"<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>" action, the Postfix SMTP server continues to look
+for opportunities to reject mail, and defers the client request
+only if it would otherwise be accepted. </p>
+
+<p> This feature is available in Postfix 2.6 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="verp_delimiter_filter">verp_delimiter_filter</a>
+(default: -=+)</b></DT><DD>
+
+<p>
+The characters Postfix accepts as VERP delimiter characters on the
+Postfix <a href="sendmail.1.html">sendmail(1)</a> command line and in SMTP commands.
+</p>
+
+<p>
+This feature is available in Postfix 1.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="virtual_alias_address_length_limit">virtual_alias_address_length_limit</a>
+(default: 1000)</b></DT><DD>
+
+<p>
+The maximal length of an email address after virtual alias expansion.
+This stops virtual aliasing loops that increase the address length
+exponentially.
+</p>
+
+<p>
+This feature is available in Postfix 3.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="virtual_alias_domains">virtual_alias_domains</a>
+(default: $<a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a>)</b></DT><DD>
+
+<p> Postfix is final destination for the specified list of virtual
+alias domains, that is, domains for which all addresses are aliased
+to addresses in other local or remote domains. The SMTP server
+validates recipient addresses with $<a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> and rejects
+non-existent recipients. See also the <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domain</a> class
+in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> file </p>
+
+<p>
+This feature is available in Postfix 2.0 and later. The default
+value is backwards compatible with Postfix version 1.1.
+</p>
+
+<p>
+The default value is $<a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> so that you can keep all
+information about <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domains</a> in one place. If you have
+many users, it is better to separate information that changes more
+frequently (virtual address -&gt; local or remote address mapping)
+from information that changes less frequently (the list of virtual
+domain names).
+</p>
+
+<p> Specify a list of host or domain names, "/file/name" or
+"<a href="DATABASE_README.html">type:table</a>" patterns, separated by commas and/or whitespace. A
+"/file/name" pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>"
+lookup table is matched when a table entry matches a lookup string
+(the lookup result is ignored). Continue long lines by starting
+the next line with whitespace. Specify "!pattern" to exclude a host
+or domain name from the list. The form "!/file/name" is supported
+only in Postfix version 2.4 and later. </p>
+
+<p>
+See also the <a href="VIRTUAL_README.html">VIRTUAL_README</a> and <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> documents
+for further information.
+</p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a> = virtual1.tld virtual2.tld
+</pre>
+
+
+</DD>
+
+<DT><b><a name="virtual_alias_expansion_limit">virtual_alias_expansion_limit</a>
+(default: 1000)</b></DT><DD>
+
+<p>
+The maximal number of addresses that virtual alias expansion produces
+from each original recipient.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="virtual_alias_maps">virtual_alias_maps</a>
+(default: $<a href="postconf.5.html#virtual_maps">virtual_maps</a>)</b></DT><DD>
+
+<p>
+Optional lookup tables that alias specific mail addresses or domains
+to other local or remote address. The table format and lookups
+are documented in <a href="virtual.5.html">virtual(5)</a>. For an overview of Postfix address
+manipulations see the <a href="ADDRESS_REWRITING_README.html">ADDRESS_REWRITING_README</a> document.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later. The default
+value is backwards compatible with Postfix version 1.1.
+</p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+Note: these lookups are recursive.
+</p>
+
+<p>
+If you use this feature with indexed files, run "<b>postmap
+/etc/postfix/virtual</b>" after changing the file.
+</p>
+
+<p>
+Examples:
+</p>
+
+<pre>
+<a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> = <a href="DATABASE_README.html#types">dbm</a>:/etc/postfix/virtual
+<a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/virtual
+</pre>
+
+
+</DD>
+
+<DT><b><a name="virtual_alias_recursion_limit">virtual_alias_recursion_limit</a>
+(default: 1000)</b></DT><DD>
+
+<p>
+The maximal nesting depth of virtual alias expansion. Currently
+the recursion limit is applied only to the left branch of the
+expansion graph, so the depth of the tree can in the worst case
+reach the sum of the expansion and recursion limits. This may
+change in the future.
+</p>
+
+<p>
+This feature is available in Postfix 2.1 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="virtual_delivery_status_filter">virtual_delivery_status_filter</a>
+(default: $<a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a>)</b></DT><DD>
+
+<p> Optional filter for the <a href="virtual.8.html">virtual(8)</a> delivery agent to change the
+delivery status code or explanatory text of successful or unsuccessful
+deliveries. See <a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a> for details. </p>
+
+<p> This feature is available in Postfix 3.0 and later. </p>
+
+
+</DD>
+
+<DT><b><a name="virtual_destination_concurrency_limit">virtual_destination_concurrency_limit</a>
+(default: $<a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a>)</b></DT><DD>
+
+<p> The maximal number of parallel deliveries to the same destination
+via the virtual message delivery transport. This limit is enforced
+by the queue manager. The message delivery transport name is the
+first field in the entry in the <a href="master.5.html">master.cf</a> file. </p>
+
+
+</DD>
+
+<DT><b><a name="virtual_destination_recipient_limit">virtual_destination_recipient_limit</a>
+(default: $<a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a>)</b></DT><DD>
+
+<p> The maximal number of recipients per message for the virtual
+message delivery transport. This limit is enforced by the queue
+manager. The message delivery transport name is the first field in
+the entry in the <a href="master.5.html">master.cf</a> file. </p>
+
+<p> Setting this parameter to a value of 1 changes the meaning of
+<a href="postconf.5.html#virtual_destination_concurrency_limit">virtual_destination_concurrency_limit</a> from concurrency per domain
+into concurrency per recipient. </p>
+
+
+</DD>
+
+<DT><b><a name="virtual_gid_maps">virtual_gid_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Lookup tables with the per-recipient group ID for <a href="virtual.8.html">virtual(8)</a> mailbox
+delivery.
+</p>
+
+<p> This parameter is specific to the <a href="virtual.8.html">virtual(8)</a> delivery agent.
+It does not apply when mail is delivered with a different mail
+delivery program. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p>
+In a lookup table, specify a left-hand side of "@domain.tld" to
+match any user in the specified domain that does not have a specific
+"user@domain.tld" entry.
+</p>
+
+<p>
+When a recipient address has an optional address extension
+(user+foo@domain.tld), the <a href="virtual.8.html">virtual(8)</a> delivery agent looks up
+the full address first, and when the lookup fails, it looks up the
+unextended address (user@domain.tld).
+</p>
+
+<p>
+Note 1: for security reasons, the <a href="virtual.8.html">virtual(8)</a> delivery agent disallows
+regular expression substitution of $1 etc. in regular expression
+lookup tables, because that would open a security hole.
+</p>
+
+<p>
+Note 2: for security reasons, the <a href="virtual.8.html">virtual(8)</a> delivery agent will
+silently ignore requests to use the <a href="proxymap.8.html">proxymap(8)</a> server. Instead
+it will open the table directly. Before Postfix version 2.2, the
+<a href="virtual.8.html">virtual(8)</a> delivery agent will terminate with a fatal error.
+</p>
+
+
+</DD>
+
+<DT><b><a name="virtual_mailbox_base">virtual_mailbox_base</a>
+(default: empty)</b></DT><DD>
+
+<p>
+A prefix that the <a href="virtual.8.html">virtual(8)</a> delivery agent prepends to all pathname
+results from $<a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a> table lookups. This is a safety
+measure to ensure that an out of control map doesn't litter the
+file system with mailboxes. While <a href="postconf.5.html#virtual_mailbox_base">virtual_mailbox_base</a> could be
+set to "/", this setting isn't recommended.
+</p>
+
+<p> This parameter is specific to the <a href="virtual.8.html">virtual(8)</a> delivery agent.
+It does not apply when mail is delivered with a different mail
+delivery program. </p>
+
+<p>
+Example:
+</p>
+
+<pre>
+<a href="postconf.5.html#virtual_mailbox_base">virtual_mailbox_base</a> = /var/mail
+</pre>
+
+
+</DD>
+
+<DT><b><a name="virtual_mailbox_domains">virtual_mailbox_domains</a>
+(default: $<a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a>)</b></DT><DD>
+
+<p> Postfix is final destination for the specified list of domains;
+mail is delivered via the $<a href="postconf.5.html#virtual_transport">virtual_transport</a> mail delivery transport.
+By default this is the Postfix <a href="virtual.8.html">virtual(8)</a> delivery agent. The SMTP
+server validates recipient addresses with $<a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a>
+and rejects mail for non-existent recipients. See also the virtual
+mailbox domain class in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> file. </p>
+
+<p> This parameter expects the same syntax as the <a href="postconf.5.html#mydestination">mydestination</a>
+configuration parameter. </p>
+
+<p>
+This feature is available in Postfix 2.0 and later. The default
+value is backwards compatible with Postfix version 1.1.
+</p>
+
+
+</DD>
+
+<DT><b><a name="virtual_mailbox_limit">virtual_mailbox_limit</a>
+(default: 51200000)</b></DT><DD>
+
+<p>
+The maximal size in bytes of an individual <a href="virtual.8.html">virtual(8)</a> mailbox or
+maildir file, or zero (no limit). </p>
+
+<p> This parameter is specific to the <a href="virtual.8.html">virtual(8)</a> delivery agent.
+It does not apply when mail is delivered with a different mail
+delivery program. </p>
+
+
+</DD>
+
+<DT><b><a name="virtual_mailbox_lock">virtual_mailbox_lock</a>
+(default: see "postconf -d" output)</b></DT><DD>
+
+<p>
+How to lock a UNIX-style <a href="virtual.8.html">virtual(8)</a> mailbox before attempting
+delivery. For a list of available file locking methods, use the
+"<b>postconf -l</b>" command.
+</p>
+
+<p> This parameter is specific to the <a href="virtual.8.html">virtual(8)</a> delivery agent.
+It does not apply when mail is delivered with a different mail
+delivery program. </p>
+
+<p>
+This setting is ignored with <b>maildir</b> style delivery, because
+such deliveries are safe without application-level locks.
+</p>
+
+<p>
+Note 1: the <b>dotlock</b> method requires that the recipient UID
+or GID has write access to the parent directory of the recipient's
+mailbox file.
+</p>
+
+<p>
+Note 2: the default setting of this parameter is system dependent.
+</p>
+
+
+</DD>
+
+<DT><b><a name="virtual_mailbox_maps">virtual_mailbox_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Optional lookup tables with all valid addresses in the domains that
+match $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>.
+</p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p>
+In a lookup table, specify a left-hand side of "@domain.tld" to
+match any user in the specified domain that does not have a specific
+"user@domain.tld" entry.
+</p>
+
+<p> The remainder of this text is specific to the <a href="virtual.8.html">virtual(8)</a> delivery
+agent. It does not apply when mail is delivered with a different
+mail delivery program. </p>
+
+<p>
+The <a href="virtual.8.html">virtual(8)</a> delivery agent uses this table to look up the
+per-recipient mailbox or maildir pathname. If the lookup result
+ends in a slash ("/"), maildir-style delivery is carried out,
+otherwise the path is assumed to specify a UNIX-style mailbox file.
+Note that $<a href="postconf.5.html#virtual_mailbox_base">virtual_mailbox_base</a> is unconditionally prepended to
+this path.
+</p>
+
+<p>
+When a recipient address has an optional address extension
+(user+foo@domain.tld), the <a href="virtual.8.html">virtual(8)</a> delivery agent looks up
+the full address first, and when the lookup fails, it looks up the
+unextended address (user@domain.tld).
+</p>
+
+<p>
+Note 1: for security reasons, the <a href="virtual.8.html">virtual(8)</a> delivery agent disallows
+regular expression substitution of $1 etc. in regular expression
+lookup tables, because that would open a security hole.
+</p>
+
+<p>
+Note 2: for security reasons, the <a href="virtual.8.html">virtual(8)</a> delivery agent will
+silently ignore requests to use the <a href="proxymap.8.html">proxymap(8)</a> server. Instead
+it will open the table directly. Before Postfix version 2.2, the
+<a href="virtual.8.html">virtual(8)</a> delivery agent will terminate with a fatal error.
+</p>
+
+
+</DD>
+
+<DT><b><a name="virtual_maps">virtual_maps</a>
+(default: empty)</b></DT><DD>
+
+<p> Optional lookup tables with a) names of domains for which all
+addresses are aliased to addresses in other local or remote domains,
+and b) addresses that are aliased to addresses in other local or
+remote domains. Available before Postfix version 2.0. With Postfix
+version 2.0 and later, this is replaced by separate controls: <a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>
+and <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a>. </p>
+
+
+</DD>
+
+<DT><b><a name="virtual_minimum_uid">virtual_minimum_uid</a>
+(default: 100)</b></DT><DD>
+
+<p>
+The minimum user ID value that the <a href="virtual.8.html">virtual(8)</a> delivery agent accepts
+as a result from $<a href="postconf.5.html#virtual_uid_maps">virtual_uid_maps</a> table lookup. Returned
+values less than this will be rejected, and the message will be
+deferred.
+</p>
+
+<p> This parameter is specific to the <a href="virtual.8.html">virtual(8)</a> delivery agent.
+It does not apply when mail is delivered with a different mail
+delivery program. </p>
+
+
+</DD>
+
+<DT><b><a name="virtual_transport">virtual_transport</a>
+(default: virtual)</b></DT><DD>
+
+<p>
+The default mail delivery transport and next-hop destination for
+final delivery to domains listed with $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>.
+This information can be overruled with the <a href="transport.5.html">transport(5)</a> table.
+</p>
+
+<p>
+Specify a string of the form <i>transport:nexthop</i>, where <i>transport</i>
+is the name of a mail delivery transport defined in <a href="master.5.html">master.cf</a>.
+The <i>:nexthop</i> destination is optional; its syntax is documented
+in the manual page of the corresponding delivery agent.
+</p>
+
+<p>
+This feature is available in Postfix 2.0 and later.
+</p>
+
+
+</DD>
+
+<DT><b><a name="virtual_uid_maps">virtual_uid_maps</a>
+(default: empty)</b></DT><DD>
+
+<p>
+Lookup tables with the per-recipient user ID that the <a href="virtual.8.html">virtual(8)</a>
+delivery agent uses while writing to the recipient's mailbox.
+</p>
+
+<p> This parameter is specific to the <a href="virtual.8.html">virtual(8)</a> delivery agent.
+It does not apply when mail is delivered with a different mail
+delivery program. </p>
+
+<p>
+Specify zero or more "type:name" lookup tables, separated by
+whitespace or comma. Tables will be searched in the specified order
+until a match is found.
+</p>
+
+<p>
+In a lookup table, specify a left-hand side of "@domain.tld"
+to match any user in the specified domain that does not have a
+specific "user@domain.tld" entry.
+</p>
+
+<p>
+When a recipient address has an optional address extension
+(user+foo@domain.tld), the <a href="virtual.8.html">virtual(8)</a> delivery agent looks up
+the full address first, and when the lookup fails, it looks up the
+unextended address (user@domain.tld).
+</p>
+
+<p>
+Note 1: for security reasons, the <a href="virtual.8.html">virtual(8)</a> delivery agent disallows
+regular expression substitution of $1 etc. in regular expression
+lookup tables, because that would open a security hole.
+</p>
+
+<p>
+Note 2: for security reasons, the <a href="virtual.8.html">virtual(8)</a> delivery agent will
+silently ignore requests to use the <a href="proxymap.8.html">proxymap(8)</a> server. Instead
+it will open the table directly. Before Postfix version 2.2, the
+<a href="virtual.8.html">virtual(8)</a> delivery agent will terminate with a fatal error.
+</p>
+
+
+</DD>
+
+</dl>
+
+</body>
+
+</html>