Add information on changing the default MTA.
PR: 37121 Submitted by: Andrew Boothman <andrew@cream.org>
This commit is contained in:
Tom Rhodes
parent
b442f1bf18
commit
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Notes:
svn2git
2020-12-08 03:00:23 +00:00
svn path=/head/; revision=12878
1 changed files with 231 additions and 15 deletions
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@ -49,6 +49,9 @@
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<listitem><para>How to block spammers from illegally using your
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mail server as a relay.</para>
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</listitem>
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<listitem><para>How to replace <application>sendmail</application>
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as your system's default mailer.</para>
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</listitem>
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<listitem><para>How to troubleshoot common mail server
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problems.</para></listitem>
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</itemizedlist>
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@ -406,22 +409,7 @@ mail.example.com</programlisting>
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restarted for it to read the changes.</para>
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</sect2>
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<sect2>
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<title><filename>/etc/mail/mailer.conf</filename></title>
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<para>The <filename>mailer.conf</filename> configuration file
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holds a table containing the real mailer that is used for the
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given action. Very old software programs would hard-code in the
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name and path to the mailer,
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<filename>/usr/sbin/sendmail</filename>, which meant they where
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incompatible with other mailers such as postfix. Today,
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<filename>/usr/sbin/sendmail</filename> is a wrapper that looks
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at <filename>/etc/mail/mailer.conf</filename> and executes the
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correct binary. When another mail transfer agent is installed
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on the system, <filename>mailer.conf</filename> should be
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updated to reflect the correct programs to execute.</para>
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</sect2>
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<sect2>
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<title><filename>/etc/mail/sendmail.cf</filename></title>
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@ -475,6 +463,234 @@ postmaster@example.com postmaster@noc.example.net
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</sect2>
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</sect1>
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<sect1 id="mail-changingmta">
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<sect1info>
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<authorgroup>
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<author>
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<firstname>Andrew</firstname>
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<surname>Boothman</surname>
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<contrib>Written by </contrib>
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</author>
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</authorgroup>
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<authorgroup>
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<author>
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<firstname>Gregory</firstname>
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<surname>Neil Shapiro</surname>
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<contrib>Information taken from e-mails written by </contrib>
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</author>
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</authorgroup>
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</sect1info>
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<title>Changing your Mail Transfer Agent</title>
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<indexterm>
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<primary>email</primary>
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<secondary>change mta</secondary>
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</indexterm>
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<para>As already mentioned, FreeBSD comes with
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<application>sendmail</application> already installed as your
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MTA (Mail Transfer Agent). Therefore by default it is
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in charge of your outgoing and incoming mail.</para>
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<para>However, for a variety of reasons, some system
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administrators want to change their system's MTA. These
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reasons range from simply wanting to try out another MTA to
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needing a specific feature or package which relies on another
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mailer. Fortunately, whatever the reason, FreeBSD makes it
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easy to make the change.</para>
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<sect2>
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<title>Install a new MTA</title>
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<para>You have a wide choice of MTAs available. A good
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starting point is the
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<link linkend="ports">FreeBSD Ports Collection</link> where
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you will be able to find many. Of course you are free to use
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any MTA you want from any location, as long as you can make
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it run under FreeBSD.</para>
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<para>Start by installing your new MTA. Once it is installed
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it gives you a chance to decide if it really fulfills your
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needs, and also gives you the opportunity to configure your
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new software before getting it to take over from
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<application>sendmail</application>. When doing this, you
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should be sure that installing the new software won't attempt
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to overwrite system binaries such as
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<filename>/usr/bin/sendmail</filename>. Otherwise, your new
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mail software has essentially been put into service before
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you have configured it.</para>
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<para>Please refer to your chosen MTA's documentation for
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information on how to configure the software you have
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chosen.</para>
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</sect2>
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<sect2>
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<title>Disable <application>sendmail</application></title>
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<para>The procedure used to start
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<application>sendmail</application> changed significantly
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between 4.5-RELEASE and 4.6-RELEASE. Therefore, the procedure
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used to disable it is subtly different.</para>
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<sect3>
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<title>FreeBSD 4.5-STABLE before 2002/4/4 and earlier
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(including 4.5-RELEASE and earlier)</title>
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<para>Enter:</para>
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<programlisting>sendmail_enable="NO"</programlisting>
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<para>into <filename>/etc/rc.conf</filename>. This will disable
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<application>sendmail</application>'s incoming mail service,
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but if <filename>/etc/mail/mailer.conf</filename> (see below)
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is not changed, <application>sendmail</application> will
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still be used to send e-mail.</para>
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</sect3>
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<sect3>
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<title>FreeBSD 4.5-STABLE after 2002/4/4
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(including 4.6-RELEASE and later)</title>
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<para>In order to completely disable
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<application>sendmail</application> you must use</para>
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<programlisting>sendmail_enable="NONE"</programlisting>
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<para>in <filename>/etc/rc.conf.</filename></para>
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<warning>
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<para>If you disable <application>sendmail</application>'s
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outgoing mail service in this way, it is important that you
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replace it with a fully working alternative mail delivery
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system. If you choose not to, system functions such as
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&man.periodic.8; will be unable to deliver their results by
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e-mail as they would normally expect to. Many parts of your
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system may expect to have a functional
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<application>sendmail</application>-compatible system. If
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applications continue to use
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<application>sendmail</application>'s binaries to try and send
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e-mail after you have disabled it, the mail may transparently
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queue forever.</para>
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</warning>
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<para>If you only want to disable
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<application>sendmail</application>'s incoming mail service,
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you should set</para>
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<programlisting>sendmail_enable="NO"</programlisting>
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<para>in <filename>/etc/rc.conf</filename>. More information on
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<application>sendmail</application>'s startup options is
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available from the &man.rc.sendmail.8; manual page.</para>
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</sect3>
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<sect2>
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<title>Running your new MTA on boot</title>
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<para>You may have a choice of two methods for running your
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new MTA on boot, again depending on what version of FreeBSD
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you are running.</para>
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<sect3>
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<title>FreeBSD 4.5-STABLE before 2002/4/11
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(including 4.5-RELEASE and earlier)</title>
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<para>Add a script to
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<filename>/usr/local/etc/rc.d/</filename> that
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ends in <filename>.sh</filename> and is executable by
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root. The script should also accept the parameters 'start'
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or 'stop'. So that you could, for example, execute
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<filename>/usr/local/etc/rc.d/supermailer.sh start</filename>
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or <filename>/usr/local/etc/rc.d/supermailer.sh stop</filename>.
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The system will call your script using 'start' when the it
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boots and using 'stop' when the it shuts down.</para>
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</sect3>
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<sect3>
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<title>FreeBSD 4.5-STABLE after 2002/4/11
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(including 4.6-RELEASE and later)</title>
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<para>With later versions of FreeBSD, you can use the
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above method or you can also set</para>
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<programlisting>mta_start_script="filename"</programlisting>
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<para>in <filename>/etc/rc.conf</filename>, where
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<replaceable>filename</replaceable> is the name of some
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script that you want executed on boot to start your
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MTA.</para>
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</sect3>
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</sect2>
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<sect2>
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<title>Replacing <application>sendmail</application> as
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the system's default mailer</title>
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<para><application>Sendmail</application> is so ubiquitous
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as standard software on Unix systems, that some software
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just presumes that it is already installed and configured.
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For this reason, many alternative MTA's provide utilities
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that implement exactly the same command-line interface
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that <application>sendmail</application> provides.</para>
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<para>Therefore, if you are using an alternative mailer,
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you will need to make sure that software trying to execute
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standard <application>sendmail</application> binaries such as
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<filename>/usr/bin/sendmail</filename> actually executes
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your chosen mailer instead. Fortunately, FreeBSD provides
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a system called &man.mailwrapper.8; that does this job for
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you.</para>
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<para>When <application>sendmail</application> is operating as installed, you will
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find something like the following
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in <filename>/etc/mail/mailer.conf</filename>:</para>
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<programlisting>sendmail /usr/libexec/sendmail/sendmail
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send-mail /usr/libexec/sendmail/sendmail
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mailq /usr/libexec/sendmail/sendmail
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newaliases /usr/libexec/sendmail/sendmail
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hoststat /usr/libexec/sendmail/sendmail
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purgestat /usr/libexec/sendmail/sendmail</programlisting>
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<para>This means that when any of these common commands
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are run, such as <filename>/usr/bin/sendmail</filename>
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the program that is actually sitting in that location
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checks <filename>mailer.conf</filename> and
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executes <filename>/usr/libexec/sendmail/sendmail</filename>
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instead. This system makes it easy to change what binaries
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are actually executed when these default system utilities
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are run.</para>
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<para>Therefore if you wanted
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<filename>/usr/local/supermailer/bin/sendmail-compat</filename>
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to be run instead of sendmail, you would change
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<filename>/etc/mail/mailer.conf</filename> to read:</para>
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<programlisting>sendmail /usr/local/supermailer/bin/sendmail-compat
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send-mail /usr/local/supermailer/bin/sendmail-compat
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mailq /usr/local/supermailer/bin/mailq-compat
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newaliases /usr/local/supermailer/bin/newaliases-compat
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hoststat /usr/local/supermailer/bin/hoststat-compat
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purgestat /usr/local/supermailer/bin/purgestat-compat</programlisting>
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</sect2>
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<sect2>
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<title>Finishing</title>
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<para>Once you have everything configured how you want it, you should
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either kill the <application>sendmail</application> processes that
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you no longer need and start the processes belonging to your new
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software. Or you should reboot your machine. Rebooting will also
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give you the opportunity to ensure that you have correctly
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configured your machine to start your new MTA on boot.</para>
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</sect2>
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</sect1>
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<sect1 id="mail-trouble">
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<title>Troubleshooting</title>
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<indexterm>
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