Mail forwarding domains

Mail forwarding domains

Some providers host domains that have no (or only a few) local mailboxes. The main purpose of these domains is to forward mail elsewhere. The following example shows how to set up 'example.com' as a mail forwarding domain usinfg postfix

 1 /etc/postfix/main.cf:
 2     virtual_alias_domains = example.com ...other hosted domains...
 3     virtual_alias_maps = hash:/etc/postfix/virtual
 4 
 5 /etc/postfix/virtual:
 6     postmaster@example.com postmaster
 7     joe@example.com        joe@somewhere
 8     jane@example.com       jane@somewhere-else
 9     # Uncomment entry below to implement a catch-all address
10     # @example.com         jim@yet-another-site
11     ...virtual aliases for more domains...

Notes:

• Line 2: The virtual_alias_domains setting tells Postfix that example.com is a so-called virtual alias domain. If you omit this setting then Postfix will reject mail (relay access denied) or will not be able to deliver it (mail for example.com loops back to myself).

NEVER list a virtual alias domain name as a mydestination domain!

• Lines 3-11: The /etc/postfix/virtual file contains the virtual aliases. With the example above, mail for postmaster@example.com goes to the local postmaster, while mail for joe@example.com goes to the remote address joe@somewhere, and mail for jane@example.com goes to the remote address jane@somewhere-else. Mail for all other addresses in example.com is rejected with the error message "User unknown".

• Line 10: The commented out entry (text after #) shows how one would implement a catch-all virtual alias that receives mail for every example.com address not listed in the virtual alias file. This is not without risk. Spammers nowadays try to send mail from (or mail to) every possible name that they can think of. A catch-all mailbox is likely to receive many spam messages, and many bounces for spam messages that were sent in the name of anything@example.com.

Execute the command

   postmap /etc/postfix/virtual" 

after changing the virtual file, and execute the command

   postfix reload 

after changing the main.cf file.

More details about the virtual alias file are given in the virtual(5) manual page, including multiple addresses on the right-hand side.