Forwarding a Postfix Virtual Alias to /dev/null

By Juliet Kemp (Send Email)
Posted Oct 19, 2009

It's poor practice to send out email from email addresses that don't resolve, and may mean your mail ends up in a spamtrap. But sometimes you want to use a "do-not-reply" type of email address, and you don't want to have to mass-delete the mailbox at intervals.

Tip of the Trade: Sometimes you want to use a "do-not-reply" type of email address and you don't want to have to mass-delete the mailbox at intervals. Here's an easy way to add a Postfix virtual alias to /dev/null.

The usual solution is to forward to /dev/null, and in a local-only setup you could do that in /etc/aliases:

do-not-reply: /dev/null
However, if you're using Postfix virtual domains, it gets a little more complicated. With virtual domains/users, you can't forward mail to a file. It must go to a user or an email address, like this:
juliet@example.com        juliet@example2.com
However, what you can do is set up an alias user in /etc/aliases:
devnull:	/dev/null
and then point to that in your virtual domain database file (which should be somewhere in /etc/postfix/virtual/, or it may be the /etc/postfix/virtual file itself):
do-not-reply@example.com	devnull
After you've made the change, run postmap /etc/postfix/virtual/dbfile and reload Postfix. You can check if the alias is properly set up with the command:
postmap -q do-not-reply@example.com /etc/postfix/virtual/dbfile
You should see the correct alias returned.

One last gotcha: On some systems, the /etc/aliases change may not work unless that user (devnull) already exists on the system. You may well already have a nobody user in /etc/passwd (one with a nonexistent home directory and no login shell), which you can use in place of devnull in /etc/aliases; otherwise you can set up a devnull user to operate similarly.

Juliet Kemp has been messing around with Linux systems, for financial reward and otherwise, for about a decade. She is also the author of "Linux System Administration Recipes: A Problem-Solution Approach" (Apress, 2009).

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