Postfix can handle e-mails from multiple domains by mapping users from one domain to the other. A good example, is a machine with multiple domain names where the actual users are the same. This short tutorial explains how to configure postfix to handle e-mail from multiple domains by using the virtual domains feature of postfix.

You can create a file name, for example, domains, in which you list all the additional domains that postfix should handle mail for:

somexample.com
somexample.net
somexample.org

and save it to, say, /etc/postfix/domains. After that, run postmap on the file:

postmap /etc/postfix/domains

When this is done, you can add the domain file to postfix's configuration by editing main.cf and appending the path to the file to the mydestination directory:

mydestination = $myhostname, /etc/postfix/domains

To map users from one domain to the other, create another file, called, say, addressmap and save it to, say, /etc/postfix/addressmap. This file should have a specific format, for example:

somexample.com              DOMAIN
joe@somexample.com          jane
jade@somexample.com         jitty

somexample.net              DOMAIN
@somexample.net             office

somexample.org              DOMAIN
@somexample.org             office

which does the following:

• it maps joe for the domain somexample.com to the local user jane
• it maps jade for the domain somexample.com to the local user jitty
• it maps all e-mails for the domain somexample.net to the local user office
• it maps all e-mails for the domain somexample.org to the local user office

Note that these mappings respect the aliases which are usually placed at /etc/aliases.

Once the addressmap file is written, you can run postmap on the file:

postmap /etc/postfix/addressmap

Finally, a reference to the file can be added to /etc/postfix/main.cf in the virtual_maps configuration key:

virtual_maps  = hash:/etc/postfix/virtual/addressmap