Parsing POP3 Mailbox

Ok, this is what I want to do. I would like to parse a mailbox and forward the returned mail in it to other users. For instance, if I send an e-mail to "you@yourdomain.com" and "you@yourdomain.com" doesn't exist it is going to send the return to "root@myserver". I want to parse "root@myserver" and send the e-mail to whoever is in the "Disposition-Notification-To" header of the e-mail. Anyone know where I can find a good script to parse mail boxes or maybe give me an idea of where to start? I checked hotscripts and some others but they are complete web based e-mail systems. I'd like to run this as a cron job if possible and I don't want to tear another system all apart if I don't have to. Thanks in advance! Brian