Postfix: mailrelay howto

This is a quick howto to enable you to relay all your Postfix mailtraffic to either your ISP’s SMTP gateway or to forward your outgoing mail to a corporate centralized gateway. This can even be done on a non standard SMTP port.

I’ve applied this configuration to an Ubuntu Server 10.04LTS.

1. Find and edit your /etc/postfix/
2. Search for the attribute ‘relayhost’
3. Add the desired server name to the relayhost:

relayhost =

4. Restart your postfix daemon:

/etc/init.d/postfix restart

Make sure your relayhost accepts incoming mail from other servers (relaying is mostly prohibited)

When you would like to change the default (incoming) port number of your relay server add :<portnumber> after the hostname of the relayhost attribute within the postfix config:

relayhost =<yourport>


The above should do the trick!


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