I've been searching for a resource on how to do this but not having much luck.
I am running a working MTA/MUA that is based on Postfix and Courier with MySQL as a backend for virtual users. I based my system on the following article:
It was great up until the empty sections! My SMTP/IMAP setup is working great, and I managed to get SpamAssassin and ClamAV installed as well with some separate documentation I found online.
What I need help with is setting up Postfix to use Procmail as the mailbox_command so that it will work with virtual users. I want to be able to define different Procmail rules for each virtual user separately. I've read the Postfix documentation, and as I understand it the default functionality for mailbox_command will only work for local (non-virtual) users.
Thanks in advance!
Since this post, I've come to realize that mailbox_command is not tenable. Instead I found a way to do this using transport_maps. Read my own answer below.