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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 Replacements for Deprecated Features </title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel='stylesheet' type='text/css' href='postfix-doc.css'>
</head>
<body>
<h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix
Replacements for Deprecated Features</h1>
<hr>
<h2>Purpose of this document </h2>
<p> This document describes Postfix features that are deprecated
(will be removed) or that have already been removed. It also has
tips for making an existing Postfix configuration more future-proof.
</p>
<p> Overview: </p>
<ul>
<li> <a href="#why"> Why deprecate? </a>
<li> <a href="#process"> Deprecation process </a>
<li> <a href="#features"> Deprecated features </a>
</ul>
<h2> <a name="why"> Why deprecate? </a> </h2>
<p> Sometimes, a Postfix feature needs to be replaced with a different
one. To give an example: </p>
<ul>
<li> <p> The initial Postfix TLS implementation used multiple boolean
parameters: one parameter to enable opportunistic TLS (for example,
"smtp_enforce_tls = yes") and one parameter to enable mandatory TLS
(for example, "smtp_require_tls = yes"). </p>
<li> <p> As we added support more features such as fingerprint,
dane, and so on, we decided not to add more boolean parameters.
Instead we introduced one configuration parameter to select from
multiple deployment models (for example, smtp_tls_security_level =
may | encrypt | dane, etc...). </p>
</ul>
<!--
<p> Over time it has become clear that 'level' is too rigid, so this may
have to change again. Wietse and Viktor have been discussing a way to
specify a range with minimum properties that are required (e.g., encrypt)
and nice-to-have properties if they are available (dane or mta-sts). </p>
-->
<p> Having both the "old" and "new" way to configure Postfix is
convenient for existing Postfix installations, because their
configuration does not break after an upgrade to a new version.
Unfortunately, there are also disadvantages. Having multiple ways
to do similar things is not only confusing for newcomers, it also
makes Postfix harder to change. </p>
<h2> <a name="process"> Deprecation process </a> </h2>
<p> The basic process steps are: </p>
<ol>
<li> <p> Inform humans that a feature will be removed, and suggest
replacements, in logging and documentation. </p>
<li> <p> Remove the feature, and update logging and documentation. </p>
</ol>
<p> Disclaimer: it has taken 20 years for some features to be
removed. This past is not a guarantee for the future. </p>
<h2> <a name="features"> Deprecated features </a> </h2>
<p> The table summarizes removed or deprecated features and
replacements. Click on the "obsolete feature" name for a more
detailed description. </p>
<blockquote>
<table border="1">
<tr> <th> Obsolete feature name </th> <th> Warning as <br> of version
</th> <th> Removed <br> in version </th> <th> Replacement </th>
</tr>
<tr> <td> <a href="#disable_dns_lookups"> disable_dns_lookups </a>
</td> <td align="center"> 3.9 </td> <td align="center"> - </td>
<td> smtp_dns_support_level </td> </tr>
<tr> <td> <a href="#xxx_enforce_tls"> <i>xxx</i>_use_tls </a> </td>
<td align="center"> 3.9 </td> <td align="center"> - </td> <td>
<i>xxx</i>_tls_security_level </td> </tr>
<tr> <td> <a href="#xxx_enforce_tls"> <i>xxx</i>_enforce_tls </a>
</td> <td align="center"> 3.9 </td> <td align="center"> - </td>
<td> <i>xxx</i>_tls_security_level </td> </tr>
<tr> <td> <a href="#xxx_per_site"> <i>xxx</i>_per_site </a> </td>
<td align="center"> 3.9 </td> <td align="center"> - </td> <td>
<i>xxx</i>_policy_maps </td> </tr>
<tr> <td> <a href="#smtpd_tls_dh1024_param_file">
smtpd_tls_dh1024_param_file </a> </td> <td align="center"> 3.9 </td>
<td align="center"> - </td> <td> do not specify (leave at default)
</td> </tr>
<tr> <td> <a href="#smtpd_tls_eecdh_grade"> smtpd_tls_eecdh_grade
</a> </td> <td align="center"> 3.9 </td> <td align="center"> - </td>
<td> do not specify (leave at default) </td> </tr>
<tr> <td> <a href="#permit_mx_backup"> permit_mx_backup </a> </td>
<td align="center"> 3.9 </td> <td align="center"> - </td> <td>
relay_domains </td> </tr>
<tr> <td> <a href="#check_relay_domains"> check_relay_domains </a>
</td> <td align="center"> 2.2 </td> <td align="center"> 3.9 </td>
<td> permit_mynetworks, reject_unauth_destination </td> </tr>
<tr> <td> <a href="#reject_maps_rbl"> reject_maps_rbl </a> </td>
<td align="center"> 2.1 </td> <td align="center"> 3.9 </td> <td>
reject_rbl_client </td> </tr>
<tr> <td> <a href="#permit_naked_ip_address"> permit_naked_ip_address
</a> </td> <td align="center"> 2.0 </td> <td align="center"> 3.9
</td> <td> permit_mynetworks, permit_sasl_authenticated </td> </tr>
</table>
</blockquote>
<h3> <a name="disable_dns_lookups"> Obsolete DNS on/off configuration
</a> </h3>
<p> The postconf(1) command logs the following: </p>
<ul>
<li> support for parameter "disable_dns_lookups" will be removed; instead, specify "smtp_dns_support_level"
</ul>
<p> Replace obsolete configuration with its replacement: </p>
<blockquote>
<table border="1">
<tr> <th width="33%"> Goal </th> <th width="33%"> Obsolete configuration
</th> <th> Replacement configuration </th> </tr>
<tr> <td> To disable DNS lookups in the Postfix SMTP/LMTP client
</td> <td> disable_dns_lookups = yes </td> <td> smtp_dns_support_level
= disabled </td> </tr>
<tr> <td> To enable DNS lookups in the Postfix SMTP/LMTP client </td> <td>
disable_dns_lookups = no </td> <td>
Leave smtp_dns_support_level at the implicit default which is empty, unless
you need a higher support level such as DNSSEC. </td> </tr>
</table>
</blockquote>
<h3> <a name="xxx_use_tls"> Obsolete opportunistic TLS configuration
</a> </h3>
<p> The postconf(1) command logs one of the following: </p>
<ul>
<li> support for parameter "lmtp_use_tls" will be removed; instead, specify "lmtp_tls_security_level"
<li> support for parameter "smtp_use_tls" will be removed; instead, specify "smtp_tls_security_level"
<li> support for parameter "smtpd_use_tls" will be removed; instead, specify "smtpd_tls_security_level"
</ul>
<p> There are similarly-named parameters and warnings for postscreen(8)
and tlsproxy(8), but those parameters should rarely be specified
by hand. </p>
<p> Replace obsolete configuration with its replacement: </p>
<blockquote>
<table border="1">
<tr> <th width="33%"> Goal </th> <th width="33%"> Obsolete configuration </th> <th> Replacement configuration </th> </tr>
<tr> <td> To turn off TLS </td> <td> <i>xxx</i>_use_tls = no </td>
<td> <i>xxx</i>_security_level = none </td> </tr>
<tr> <td> To turn on opportunistic TLS </td> <td> <i>xxx</i>_use_tls
= yes </td> <td> <i>xxx</i>_security_level = may </td> </tr>
</table>
</blockquote>
<h3> <a name="xxx_enforce_tls"> Obsolete mandatory TLS configuration
</a> </h3>
<p> The postconf(1) command logs one of the following: </p>
<ul>
<li> support for parameter "lmtp_enforce_tls" will be removed; instead, specify "lmtp_tls_security_level"
<li> support for parameter "smtp_enforce_tls" will be removed; instead, specify "smtp_tls_security_level"
<li> support for parameter "smtpd_enforce_tls" will be removed; instead, specify "smtpd_tls_security_level"
</ul>
<p> There are similarly-named parameters and warnings for postscreen(8)
and tlsproxy(8), but those parameters should rarely be specified
by hand. </p>
<p> Replace obsolete configuration with its replacement: </p>
<blockquote>
<table border="1">
<tr> <th width="33%"> Goal </th> <th width="33%"> Obsolete configuration </th> <th> Replacement configuration </th> </tr>
<tr> <td> To turn off mandatory TLS </td> <td> <i>xxx</i>_enforce_tls
= no </td> <td> <i>xxx</i>_security_level = may </td> </tr>
<tr> <td> To turn on mandatory TLS </td> <td> <i>xxx</i>_enforce_tls
= yes </td> <td> <i>xxx</i>_security_level = encrypt </td> </tr>
</table>
</blockquote>
<h3> <a name="xxx_per_site"> Obsolete TLS policy table configuration
</a> </h3>
<p> The postconf(1) command logs one of the following: </p>
<ul>
<li> support for parameter "lmtp_tls_per_site" will be removed;
instead, specify "lmtp_tls_policy_maps"
<li> support for parameter "smtp_tls_per_site" will be removed;
instead, specify "smtp_tls_policy_maps"
</ul>
<p> There is similarly-named parameter and warning for tlsproxy(8),
but that parameter should rarely be specified by hand. </p>
<p> Unfortunately, this is more than a name change: the table format
has changed too, as has the table search process. There is no simple
conversion of the obsolete form to its replacement. </p>
<h3> <a name="check_relay_domains"> check_relay_domains </a> </h3>
<p> Depending on the Postfix version, the Postfix SMTP daemon logs
following warning: </p>
<ul>
<li> support for restriction "check_relay_domains" has been removed
in Postfix 3.9"; instead, specify "reject_unauth_destination"
<li> support for restriction "check_relay_domains" will be removed
from Postfix; use "reject_unauth_destination" instead
</ul>
<p> This feature was removed because it would relay based on the
client domain name, which is not robust. </p>
<p> Recommended configuration to prevent an "open relay" problem
with the SMTP service on port 25:
</p>
<blockquote>
<pre>
main.cf:
smtpd_recipient_restrictions =
permit_mynetworks,
permit_sasl_authenticated,
reject_unauth_destination
...other restrictions...
</pre>
</blockquote>
<p> Or equivalent in smtpd_relay_restrictions. </p>
<h3> <a name="permit_mx_backup"> permit_mx_backup</a> </h3>
<p> The Postfix version 3.9 and later SMTP daemon logs the following
warning: </p>
<ul>
<li> support for restriction "permit_mx_backup" will be removed
from Postfix; instead, specify "relay_domains"
</ul>
<p> This feature will be removed because it is too difficult to
configure recipient address validation, making Postfix a source of
backscatter bounces. </p>
<p> To specify the domains that Postfix will provide MX backup
service for, see <a href="STANDARD_CONFIGURATION_README.html#backup">
Configuring Postfix as primary or backup MX host for a remote
site</a>. </p>
<h3> <a name="reject_maps_rbl"> reject_maps_rbl</a> </h3>
<p> Depending on the Postfix version, the SMTP daemon logs one of
the following warnings: </p>
<ul>
<li> support for restriction "reject_maps_rbl" has been removed in
Postfix 3.9"; instead, specify "reject_rbl_client domain-name"
<li> support for restriction "reject_maps_rbl" will be removed from
Postfix; use "reject_rbl_client domain-name" instead
</ul>
<p> This feature was replaced because "MAPS RBL" is the name of a
specific reputation service. The reject_rbl_client feature provides
a superset of the reject_maps_rbl functionality. </p>
<p> Recommended configuration: </p>
<blockquote>
<pre>
main.cf:
smtpd_recipient_restrictions =
permit_mynetworks,
permit_sasl_authenticated,
reject_unauth_destination
reject_rbl_client <i>domain-name</i>
...other restrictions...
</pre>
</blockquote>
<p> Where <i>domain-name</i> is the domain name of a DNS reputation service. </p>
<h3> <a name="permit_naked_ip_address"> permit_naked_ip_address</a> </h3>
<p> Depending on the Postfix version, the SMTP daemon logs one of
the following warnings: </p>
<ul>
<li> support for restriction "permit_naked_ip_address" has been
removed in Postfix 3.9"; instead, specify "permit_mynetworks" or
"permit_sasl_authenticated"
<li> restriction permit_naked_ip_address is deprecated. Use
permit_mynetworks or permit_sasl_authenticated instead
</ul>
<p> This feature was removed because it was easy to get a false
match when smtpd_recipient_restrictions was intended to match a
remote SMTP client IP address. </p>
<p> Recommended configuration: </p>
<blockquote>
<pre>
main.cf:
smtpd_recipient_restrictions =
permit_mynetworks,
permit_sasl_authenticated,
reject_unauth_destination
reject_rbl_client <i>domain-name</i>
...other restrictions...
</pre>
</blockquote>
<p> That is, no restriction on HELO or EHLO syntax. Such restrictions
ar rarely useful nowadays.
</body>
</html>
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