Depending on your situation, it may be handy to redirect e-mails that have a certain subject line before it even reaches a user's inbox. Let's say you're tired of getting e-mails that start with the word "Cialis". Just follow these steps to redirect those e-mails.
First, enable header checks in /etc/postfix/main.cf:
header_checks = regexp:/etc/postfix/header_checks
Then, create /etc/postfix/header_checks and add the following:
/^Subject: Jobs*/
REDIRECT someotheruser@domain.com
For a lot more information about header checks in postfix, review the documentation here:
http://www.postfix.org/header_checks.5.html
