Adding additional SMTP listener ports

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The ZCS MTA can be configured to accept mail traffic on additional SMTP service ports. This means more than one TCP port can be used to bind to the SMTP daemon.

For ZCS servers listening on the default port of 25, /opt/zimbra/postfix/conf/master.cf.in contains this line:

   smtp      inet  n       -       n       -       -       smtpd

To add an additional listener port of 2525, insert the the following after the above:

   2525      inet  n       -       n       -       -       smtpd

Then, restart the MTA:

   # su - zimbra
   # zmmtactl stop
   # zmmtactl start


SMTP SSL

  • As of ZCS v4.0.x, the default Zimbra postfix config does not have TLS enabled on separate port. If you want postfix to listen on different port for TLS (ie. SMTPS, as defined in /etc/services -- port #465), you'll need the comment out the line beginning with "smtps ...." in /opt/zimbra/postfix/conf/master.cf.
 smtps    inet  n       -       n       -       -       smtpd
   -o smtpd_tls_wrappermode=yes -o smtpd_sasl_auth_enable=yes

NOTE - that's TWO lines, and the second line MUST begin with whitespace

Caveats

  • Do not attempt to bind to ports in use by other applications. This will cause the MTA or other application to fail.
  • Backup /opt/zimbra/postfix/master.cf before an upgrade. Changes made to master.cf should only be applied to the current distribution after upgrading.
  • Any changes to Postfix 'master.cf' will require restart steps detailed above.
  • There was a recent change that included master.cf.in. Any permanent changes should be made to the master.cf.in file.
Verified Against: unknown Date Created: 07/17/2006
Article ID: http://wiki.zimbra.com/index.php?title=Adding_additional_SMTP_listener_ports Date Modified: 08/5/2009
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