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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 12:06:34 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 12:06:34 +0000
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parentInitial commit. (diff)
downloadpostfix-upstream/3.5.24.tar.xz
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Adding upstream version 3.5.24.upstream/3.5.24upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN"
+ "http://www.w3.org/TR/html4/loose.dtd">
+
+<html>
+
+<head>
+
+<title>Postfix Small/Home Office Hints and Tips</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 Small/Home Office Hints and Tips</h1>
+
+<hr>
+
+<h2>Overview</h2>
+
+<p> This document combines hints and tips for "small office/home
+office" applications into one document so that they are easier to
+find. The text describes the mail sending side only. If your machine
+does not receive mail directly (i.e. it does not have its own
+Internet domain name and its own fixed IP address), then you will
+need a solution such as "fetchmail", which is outside the scope of
+the Postfix documentation. </p>
+
+<ul>
+
+<li> <p> Selected topics from the <a href="STANDARD_CONFIGURATION_README.html">STANDARD_CONFIGURATION_README</a> document: </p>
+
+<ul>
+
+<li><a href="#stand_alone">Postfix on a stand-alone Internet host</a>
+
+<li><a href="#fantasy">Postfix on hosts without a real
+Internet hostname</a>
+
+</ul>
+
+<p> Selected topics from the <a href="SASL_README.html">SASL_README</a> document: </p>
+
+<ul>
+
+<li><a href="#client_sasl_enable">Enabling SASL authentication in the
+Postfix SMTP client</a></li>
+
+<li><a href="#client_sasl_sender">Configuring Sender-Dependent SASL
+authentication </a></li>
+
+</ul>
+
+</ul>
+
+<p> See the <a href="SASL_README.html">SASL_README</a> and <a href="STANDARD_CONFIGURATION_README.html">STANDARD_CONFIGURATION_README</a> documents for
+further information on these topics. </p>
+
+<h2><a name="stand_alone">Postfix on a stand-alone Internet host</a></h2>
+
+<p> Postfix should work out of the box without change on a stand-alone
+machine that has direct Internet access. At least, that is how
+Postfix installs when you download the Postfix source code via
+<a href="http://www.postfix.org/">http://www.postfix.org/</a>. </p>
+
+<p> You can use the command "<b>postconf -n</b>" to find out what
+settings are overruled by your <a href="postconf.5.html">main.cf</a>. Besides a few pathname
+settings, few parameters should be set on a stand-alone box, beyond
+what is covered in the <a href="BASIC_CONFIGURATION_README.html">BASIC_CONFIGURATION_README</a> document: </p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ # Optional: send mail as user@domainname instead of user@hostname.
+ #<a href="postconf.5.html#myorigin">myorigin</a> = $<a href="postconf.5.html#mydomain">mydomain</a>
+
+ # Optional: specify NAT/proxy external address.
+ #<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a> = 1.2.3.4
+
+ # Alternative 1: don't relay mail from other hosts.
+ <a href="postconf.5.html#mynetworks_style">mynetworks_style</a> = host
+ <a href="postconf.5.html#relay_domains">relay_domains</a> =
+
+ # Alternative 2: relay mail from local clients only.
+ # <a href="postconf.5.html#mynetworks">mynetworks</a> = 192.168.1.0/28
+ # <a href="postconf.5.html#relay_domains">relay_domains</a> =
+</pre>
+</blockquote>
+
+<p> See also the section "<a href="#fantasy">Postfix on hosts without
+a real Internet hostname</a>" if this is applicable to your configuration.
+</p>
+
+<h2><a name="fantasy">Postfix on hosts without a real Internet
+hostname</a></h2>
+
+<p> This section is for hosts that don't have their own Internet
+hostname. Typically these are systems that get a dynamic IP address
+via DHCP or via dialup. Postfix will let you send and receive mail
+just fine between accounts on a machine with a fantasy name. However,
+you cannot use a fantasy hostname in your email address when sending
+mail into the Internet, because no-one would be able to reply to
+your mail. In fact, more and more sites refuse mail addresses with
+non-existent domain names. </p>
+
+<p> Note: the following information is Postfix version dependent.
+To find out what Postfix version you have, execute the command
+"<b>postconf <a href="postconf.5.html#mail_version">mail_version</a></b>". </p>
+
+<h3>Solution 1: Postfix version 2.2 and later </h3>
+
+<p> Postfix 2.2 uses the <a href="generic.5.html">generic(5)</a> address mapping to replace
+local fantasy email addresses by valid Internet addresses. This
+mapping happens ONLY when mail leaves the machine; not when you
+send mail between users on the same machine. </p>
+
+<p> The following example presents additional configuration. You
+need to combine this with basic configuration information as
+discussed the first half of this document. </p>
+
+<blockquote>
+<pre>
+1 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
+2 <a href="postconf.5.html#smtp_generic_maps">smtp_generic_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/generic
+3
+4 /etc/postfix/generic:
+5 his@localdomain.local hisaccount@hisisp.example
+6 her@localdomain.local heraccount@herisp.example
+7 @localdomain.local hisaccount+local@hisisp.example
+</pre>
+</blockquote>
+
+<p> When mail is sent to a remote host via SMTP: </p>
+
+<ul>
+
+<li> <p> Line 5 replaces <i>his@localdomain.local</i> by his ISP
+mail address, </p>
+
+<li> <p> Line 6 replaces <i>her@localdomain.local</i> by her ISP
+mail address, and </p>
+
+<li> <p> Line 7 replaces other local addresses by his ISP account,
+with an address extension of +<i>local</i> (this example assumes
+that the ISP supports "+" style address extensions). </p>
+
+</ul>
+
+<p>Specify <b>dbm</b> instead of <b>hash</b> if your system uses
+<b>dbm</b> files instead of <b>db</b> files. To find out what lookup
+tables Postfix supports, use the command "<b>postconf -m</b>". </p>
+
+<p> Execute the command "<b>postmap /etc/postfix/generic</b>"
+whenever you change the generic table. </p>
+
+<h3>Solution 2: Postfix version 2.1 and earlier </h3>
+
+<p> The solution with older Postfix systems is to use valid
+Internet addresses where possible, and to let Postfix map valid
+Internet addresses to local fantasy addresses. With this, you can
+send mail to the Internet and to local fantasy addresses, including
+mail to local fantasy addresses that don't have a valid Internet
+address of their own.</p>
+
+<p> The following example presents additional configuration. You
+need to combine this with basic configuration information as
+discussed the first half of this document. </p>
+
+<blockquote>
+<pre>
+ 1 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ 2 <a href="postconf.5.html#myhostname">myhostname</a> = hostname.localdomain
+ 3 <a href="postconf.5.html#mydomain">mydomain</a> = localdomain
+ 4
+ 5 <a href="postconf.5.html#canonical_maps">canonical_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/canonical
+ 6
+ 7 <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/virtual
+ 8
+ 9 /etc/postfix/canonical:
+10 your-login-name your-account@your-isp.com
+11
+12 /etc/postfix/virtual:
+13 your-account@your-isp.com your-login-name
+</pre>
+</blockquote>
+
+<p> Translation: </p>
+
+<ul>
+
+<li> <p> Lines 2-3: Substitute your fantasy hostname here. Do not
+use a domain name that is already in use by real organizations
+on the Internet. See <a href="http://tools.ietf.org/html/rfc2606">RFC 2606</a> for examples of domain
+names that are guaranteed not to be owned by anyone. </p>
+
+<li> <p> Lines 5, 9, 10: This provides the mapping from
+"your-login-name@hostname.localdomain" to "your-account@your-isp.com".
+This part is required. </p>
+
+<li> <p> Lines 7, 12, 13: Deliver mail for "your-account@your-isp.com"
+locally, instead of sending it to the ISP. This part is not required
+but is convenient.
+
+</ul>
+
+<p>Specify <b>dbm</b> instead of <b>hash</b> if your system uses
+<b>dbm</b> files instead of <b>db</b> files. To find out what lookup
+tables Postfix supports, use the command "<b>postconf -m</b>". </p>
+
+<p> Execute the command "<b>postmap /etc/postfix/canonical</b>"
+whenever you change the canonical table. </p>
+
+<p> Execute the command "<b>postmap /etc/postfix/virtual</b>"
+whenever you change the virtual table. </p>
+
+<h2><a name="client_sasl_enable">Enabling SASL authentication in the
+Postfix SMTP/LMTP client</a></h2>
+
+<p> This section shows a typical scenario where the Postfix SMTP
+client sends all messages via a mail gateway server that requires
+SASL authentication. </p>
+
+<blockquote>
+
+<strong> Trouble solving tips: </strong>
+
+<ul>
+
+<li> <p> If your SASL logins fail with "SASL authentication failure:
+No worthy mechs found" in the mail logfile, then see the section
+"<a href="SASL_README.html#client_sasl_policy">Postfix SMTP/LMTP
+client policy - SASL mechanism <em>properties</em></a>".
+
+<li> <p> For a solution to a more obscure class of SASL authentication
+failures, see "<a href="SASL_README.html#client_sasl_filter">Postfix
+SMTP/LMTP client policy - SASL mechanism <em>names</em></a>".
+
+</ul>
+
+</blockquote>
+
+<p> To make the example more readable we introduce it in two parts.
+The first part takes care of the basic configuration, while the
+second part sets up the username/password information. </p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtp_sasl_auth_enable">smtp_sasl_auth_enable</a> = yes
+ <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = encrypt
+ <a href="postconf.5.html#smtp_sasl_tls_security_options">smtp_sasl_tls_security_options</a> = noanonymous
+ <a href="postconf.5.html#relayhost">relayhost</a> = [mail.isp.example]
+ # Alternative form:
+ # <a href="postconf.5.html#relayhost">relayhost</a> = [mail.isp.example]:submission
+ <a href="postconf.5.html#smtp_sasl_password_maps">smtp_sasl_password_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/sasl_passwd
+</pre>
+</blockquote>
+
+<ul>
+
+<li> <p> The <code><a href="postconf.5.html#smtp_sasl_auth_enable">smtp_sasl_auth_enable</a></code> setting enables
+client-side authentication. We will configure the client's username
+and password information in the second part of the example. </p>
+</li>
+
+<li> <p> The <code><a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a></code> setting ensures
+that the connection to the remote smtp server will be encrypted, and
+<code><a href="postconf.5.html#smtp_sasl_tls_security_options">smtp_sasl_tls_security_options</a></code> removes the prohibition on
+plaintext passwords. </p>
+
+<li> <p> The <code><a href="postconf.5.html#relayhost">relayhost</a></code> setting forces the Postfix SMTP
+to send all remote messages to the specified mail server instead
+of trying to deliver them directly to their destination. </p> </li>
+
+<li> <p> In the <code><a href="postconf.5.html#relayhost">relayhost</a></code> setting, the "<code>[</code>"
+and "<code>]</code>" prevent the Postfix SMTP client from looking
+up MX (mail exchanger) records for the enclosed name. </p> </li>
+
+<li> <p> The <code><a href="postconf.5.html#relayhost">relayhost</a></code> destination may also specify a
+non-default TCP port. For example, the alternative form
+<code>[mail.isp.example]:submission</code> tells Postfix to connect
+to TCP network port 587, which is reserved for email client
+applications. </p> </li>
+
+<li> <p> The Postfix SMTP client is compatible with SMTP servers
+that use the non-standard "<code>AUTH=<em>method.</em>...</code>"
+syntax in response to the EHLO command; this requires no additional
+Postfix client configuration. </p> </li>
+
+<li> <p> The Postfix SMTP client does not support the obsolete
+"wrappermode" protocol, which uses TCP port <code>465</code> on the
+SMTP server. See <a href="TLS_README.html">TLS_README</a> for a solution that uses the
+<code>stunnel</code> command. </p> </li>
+
+<li> <p> With the <code><a href="postconf.5.html#smtp_sasl_password_maps">smtp_sasl_password_maps</a></code> parameter,
+we configure the Postfix SMTP client to send username and password
+information to the mail gateway server. As discussed in the next
+section, the Postfix SMTP client supports multiple ISP accounts.
+For this reason the username and password are stored in a table
+that contains one username/password combination for each mail gateway
+server. </p>
+
+</ul>
+
+<blockquote>
+<pre>
+/etc/postfix/sasl_passwd:
+ # destination credentials
+ [mail.isp.example] username:password
+ # Alternative form:
+ # [mail.isp.example]:submission username:password
+</pre>
+</blockquote>
+
+<blockquote>
+
+<strong>Important</strong>
+
+<p> Keep the SASL client password file in <code>/etc/postfix</code>,
+and make the file read+write only for <code>root</code> to protect
+the username/password combinations against other users. The Postfix
+SMTP client will still be able to read the SASL client passwords.
+It opens the file as user <code>root</code> before it drops privileges,
+and before entering an optional chroot jail. </p>
+
+</blockquote>
+
+<ul>
+
+<li> <p> Use the <code>postmap</code> command whenever you
+change the <code>/etc/postfix/sasl_passwd</code> file. </p> </li>
+
+<li> <p> If you specify the "<code>[</code>" and "<code>]</code>"
+in the <code><a href="postconf.5.html#relayhost">relayhost</a></code> destination, then you must use the
+same form in the <code><a href="postconf.5.html#smtp_sasl_password_maps">smtp_sasl_password_maps</a></code> file. </p>
+</li>
+
+<li> <p> If you specify a non-default TCP Port (such as
+"<code>:submission</code>" or "<code>:587</code>") in the
+<code><a href="postconf.5.html#relayhost">relayhost</a></code> destination, then you must use the same form
+in the <code><a href="postconf.5.html#smtp_sasl_password_maps">smtp_sasl_password_maps</a></code> file. </p> </li>
+
+</ul>
+
+<h2><a name="client_sasl_sender">Configuring Sender-Dependent SASL
+authentication</a></h2>
+
+<p> Postfix supports different ISP accounts for different sender
+addresses (version 2.3 and later). This can be useful when one
+person uses the same machine for work and for personal use, or when
+people with different ISP accounts share the same Postfix server.
+</p>
+
+<p> To make this possible, Postfix supports per-sender SASL passwords
+and per-sender relay hosts. In the example below, the Postfix SMTP
+client will search the SASL password file by sender address before
+it searches that same file by destination. Likewise, the Postfix
+<a href="trivial-rewrite.8.html">trivial-rewrite(8)</a> daemon will search the per-sender <a href="postconf.5.html#relayhost">relayhost</a> file,
+and use the default <code><a href="postconf.5.html#relayhost">relayhost</a></code> setting only as a final
+resort. </p>
+
+<blockquote>
+<pre>
+/etc/postfix/<a href="postconf.5.html">main.cf</a>:
+ <a href="postconf.5.html#smtp_sender_dependent_authentication">smtp_sender_dependent_authentication</a> = yes
+ <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/sender_relay
+ <a href="postconf.5.html#smtp_sasl_auth_enable">smtp_sasl_auth_enable</a> = yes
+ <a href="postconf.5.html#smtp_sasl_password_maps">smtp_sasl_password_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/sasl_passwd
+ <a href="postconf.5.html#relayhost">relayhost</a> = [mail.isp.example]
+ # Alternative form:
+ # <a href="postconf.5.html#relayhost">relayhost</a> = [mail.isp.example]:submission
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/sasl_passwd:
+ # Per-sender authentication; see also /etc/postfix/sender_relay.
+ user1@example.com username1:password1
+ user2@example.net username2:password2
+ # Login information for the default <a href="postconf.5.html#relayhost">relayhost</a>.
+ [mail.isp.example] username:password
+ # Alternative form:
+ # [mail.isp.example]:submission username:password
+</pre>
+</blockquote>
+
+<blockquote>
+<pre>
+/etc/postfix/sender_relay:
+ # Per-sender provider; see also /etc/postfix/sasl_passwd.
+ user1@example.com [mail.example.com]:submission
+ user2@example.net [mail.example.net]
+</pre>
+</blockquote>
+
+<ul>
+
+<li> <p> If you are creative, then you can try to combine the two
+tables into one single MySQL database, and configure different
+Postfix queries to extract the appropriate information. </p>
+
+<li> <p> Specify dbm instead of hash if your system uses dbm files
+instead of db files. To find out what lookup tables Postfix supports,
+use the command "postconf -m". </p>
+
+<li> <p> Execute the command "postmap /etc/postfix/sasl_passwd"
+whenever you change the sasl_passwd table. </p>
+
+<li> <p> Execute the command "postmap /etc/postfix/sender_relay"
+whenever you change the sender_relay table. </p>
+
+</ul>
+
+</body>
+
+</html>