210 lines
7 KiB
HTML
210 lines
7 KiB
HTML
<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN"
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"https://www.w3.org/TR/html4/loose.dtd">
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<title>Rejecting Unknown Local Recipients with Postfix</title>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link rel='stylesheet' type='text/css' href='postfix-doc.css'>
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</head>
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<body>
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<h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Rejecting Unknown Local Recipients with Postfix</h1>
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<hr>
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<h2>Introduction</h2>
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<p> As of Postfix version 2.0, the Postfix SMTP server rejects mail
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for unknown recipients in local domains (domains that match
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$mydestination or the IP addresses in $inet_interfaces or
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$proxy_interfaces) with "User unknown in local recipient table".
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This feature was optional with earlier Postfix versions. </p>
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<p> The good news is that this keeps undeliverable mail out of your
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queue, so that your mail queue is not clogged up with undeliverable
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MAILER-DAEMON messages. </p>
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<p> The bad news is that it may cause mail to be rejected when you
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upgrade from a Postfix system that was not configured to reject
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mail for unknown local recipients. </p>
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<p> This document describes what steps are needed in order to reject
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unknown local recipients correctly. </p>
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<ul>
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<li><a href="#main_config">Configuring local_recipient_maps
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in main.cf</a>
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<li><a href="#change">When you need to change the local_recipient_maps
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setting in main.cf</a>
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<li><a href="#format">Local recipient table query format </a>
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</ul>
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<h2><a name="main_config">Configuring local_recipient_maps
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in main.cf</a></h2>
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<p> The local_recipient_maps parameter specifies lookup tables with
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all names or addresses of local recipients. A recipient address is
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local when its domain matches $mydestination, $inet_interfaces or
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$proxy_interfaces. If a local username or address is not listed in
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$local_recipient_maps, then the Postfix SMTP server will reject
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the address with "User unknown in local recipient table". Other
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interfaces such as the Postfix sendmail(1) command may still accept
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an "unknown" recipient. </p>
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<p> The default setting, shown below, assumes that you use the
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default Postfix local(8) delivery agent for local delivery, where
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recipients are either UNIX accounts (typically, in /etc/passwd) or
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local aliases (typically, in /etc/aliases): </p>
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<blockquote>
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<pre>
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/etc/postfix/main.cf:
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local_recipient_maps = proxy:unix:passwd.byname $alias_maps
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</pre>
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</blockquote>
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<p> To turn off unknown local recipient rejects by the SMTP server,
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specify: </p>
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<blockquote>
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<pre>
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/etc/postfix/main.cf:
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local_recipient_maps =
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</pre>
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</blockquote>
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<p> That is, an empty value. With this setting, the Postfix SMTP
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server will not reject mail with "User unknown in local recipient
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table". <b> Don't do this on systems that receive mail directly
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from the Internet. With today's worms and viruses, Postfix will
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become a backscatter source: it accepts mail for non-existent
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recipients and then tries to return that mail as "undeliverable"
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to the often forged sender address</b>. </p>
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<h2><a name="change">When you need to change the local_recipient_maps
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setting in main.cf</a></h2>
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<ul>
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<li> <p> Problem: you don't use the default Postfix local(8)
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delivery agent for domains matching $mydestination, $inet_interfaces,
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or $proxy_interfaces. For example, you redefined the
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"local_transport" setting in main.cf. </p>
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<p> Solution: your local_recipient_maps setting needs to specify
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a database that lists all the known user names or addresses
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for that delivery agent. For example, if you deliver users in
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$mydestination etc. domains via the virtual(8) delivery agent,
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specify: </p>
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<pre>
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/etc/postfix/main.cf
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mydestination = $myhostname localhost.$mydomain localhost ...
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local_transport = virtual
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local_recipient_maps = $virtual_mailbox_maps
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</pre>
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<p> If you don't use the local(8) or virtual(8) delivery agent
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for $mydestination
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etc. domains, see the section "<a href="#format">Local recipient
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table format</a>" below for a description of how the table
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should be populated. </p>
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<li> <p> Problem: you use the mailbox_transport or fallback_transport
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feature of the Postfix local(8) delivery agent in order to
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deliver mail to non-UNIX recipients. </p>
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<p> Solution: you need to add the database that lists the
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non-UNIX recipients: </p>
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<pre>
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/etc/postfix/main.cf
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local_recipient_maps = proxy:unix:passwd.byname, $alias_maps,
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<the database with non-UNIX recipients>
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</pre>
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<p> See the section "<a href="#format">Local recipient table
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format</a>" below for a description of how the table should be
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populated. </p>
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<li> <p> Problem: you use the luser_relay feature of the Postfix
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local delivery agent. </p>
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<p> Solution: you must disable the local_recipient_maps feature
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completely, so that the Postfix SMTP server accepts mail for
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all local addresses: </p>
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<pre>
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/etc/postfix/main.cf
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local_recipient_maps =
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</pre>
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</ul>
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<h2><a name="format">Local recipient table query format</a> </h2>
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<p> If local_recipient_maps specifies local files, such as files in
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postmap(1) or postalias(1) format, then the Postfix SMTP server
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generates the following queries: </p>
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<ul>
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<li> <p> The full recipient address. This query supports a non-default
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local_transport setting with a delivery agent such as lmtp(8) or
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virtual(8). See "<a href="#main_config">Configuring local_recipient_maps
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in main.cf</a>: for additional guidance for what lookup tables to
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specify. </p>
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<li> <p> The recipient address local-part. This query supports the
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default local_transport setting with the UNIX-compatible local(8)
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delivery agent; the Postfix SMTP server makes this query only when
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the recipient domain matches $mydestination, $inet_interfaces or
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$proxy_interfaces. </p>
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<li> <p> The recipient @domain. This query supports a non-default
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local_transport setting with a delivery agent such as virtual(8);
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it is a wildcard for domains that do not have a valid recipient
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list. </p>
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</ul>
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<p> NOTES: </p>
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<ul>
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<li> <p> A lookup table should return a non-empty result when the
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address exists, and should return "not found" when the address does
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not exist. In particular, a zero-length (empty) result does not
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count as a "not found" result. </p>
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<li> <p> When local_recipient_maps specifies a lookup table based
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on ldap:, memcache:, mongodb:, mysql:, pgsql:, sqlite:, or other
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external database, then the Postfix SMTP server queries that lookup
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table with the same queries as described at the start of this
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section, and expects the same results. </p>
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<li> <p> To suppress lookups for the <i>local-part</i> and the
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<i>@domain</i> wild-card, specify the <b>domain</b> setting in a
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Postfix ldap:, memcache:, mongodb:, mysql:, pgsql:, sqlite:, etc.,
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database client configuration file. </p>
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<li> <p> When local_recipient_maps specifies a lookup table based
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on pcre:, regexp:, socketmap: or tcp:, Postfix queries that table
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only with the full recipient address, and not with the <i>local-part</i>
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or the <i>@domain</i> wild-card. </p>
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</ul>
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</body>
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</html>
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