How to get all your mail going out of one IP address with POSTFIX

If you have multiple IPs (ETH0,ETH0:0, etc) running on a server with Postfix, chances are you are going to run into the problem of Postfix not using the mail IP that has the matching MX record to send mail.

When this happens most of the mail servers will label your mail as SPAM and/or reject it.

You can force Postfix to use the main servers IP address by adding the following lines to your /etc/postfix/main.cf:
smtp_bind_address = 1.1.1.1

*You would replace 1.1.1.1 with the main IP of your own server.
Restart Postfix with /etc/init.d/postfix restart

This might cause your mail to backup on the server if your have other services  that might need a configuration tweak to continue working correctly, check your mail queue with this:
postqueue -p

If you see mail backing up in that queue for failed connections to 127.0.0.1, then you might have to start making some tweaks. If not, then you should be OK.


If you have AMAVIS running on the server then you might need to make this tweak for AMAVIS to properly work. Create the file /etc/amavis/conf.d/60-custom. Add the following line:
@inet_acl = qw( 127.0.0.1 [::1] 1.1.1.1 );

Restart AMAVIS with /etc/init.d/amavis restart

Now check the Postfix queue with postqueue -p again. If there is any mail still there try flushing it out with postqueue -f. The recheck it after a couple of seconds with postqueue -p again. It should be all gone now.