Hi there, I have just finished similar project on debian. Look at my profile, you will see. I am referring to you different configuration which I can setup without any problem in 3 days with testing: qmail+vpopmail+mysql+procmail+spamassassin+clamav+some www interface.
If you are interested let me know. If you insist on your configuration with postfix let me also know ;).
I do not make working installation, I do not take any money!
Bear in mind that debian not always has packages configured appropriately for your setup. Sometimes it is required to compile from sources to get some options.
Keeper