**caveat** Okay, before the argument of whether this is good or bad morally, I am only interested on doing this to my personal server.

I'm running SuSE 9.1 with Qmail. I want to filter all outgoing email, only allowing those emails that contain a specific header through to the "outside" world, and sending the rest to the bit bucket. Can I send mail to procmail for filtering some how? I'm familiar with Postfix but I don't think that'll help me much here, this is a rented "Plesk" server, so I'm pretty much stuck with whats installed.

Regards,
Doug

You can do it with amavisd-new..

Put it before the qmail server, listening on 25, filter the headers then pass the ok ones to qmail.
Procmail is better suited to mangling before a local file system gets the message.