Setting Up Postfix As A Backup MX

Version 1.0
Author: Falko Timme <ft [at] falkotimme [dot] com>
Last edited 06/06/2007

In this tutorial I will show how you can set up a Postfix mailserver as a backup mail exchanger for a domain so that it accepts mails for this domain in case the primary mail exchanger is down or unreachable, and passes the mails on to the primary MX once that one is up again.

I do not issue any guarantee that this will work for you!

1 Preliminary Note

I want to set up a backup MX for the domain example.com. In this example the primary MX for example.com is called mx1.example.com (IP address 1.2.3.4), so I call the backup MX mx2.example.com (IP address 1.2.3.5).

I have created MX records for example.com that look like this:

example.com.               86400   IN      MX      10 mx1.example.com.
example.com.               86400   IN      MX      20 mx2.example.com.

It’s important that the primary MX has a lower number (10) and therefore a higher priority than the backup MX (20).

I’m assuming that the Postfix on mx2.example.com is already installed and working.

Read more at Howtoforge.com

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