Not to be a commercial or anything, but I just finished installing RAV
Antivirus for Mail servers ( http://www.rav.ro ) and it works GREAT!  It
integrates with Postfix seamlessly, and also works with CommuniGate Pro,
Sendmail LIBMilter, Sendmail (any version), Qmail.

It scans and cleans incoming and outgoing SMTP traffic, attachments, subject
lines, filenames, etc.  It updates its virus definition files automatically,
cleans, quarrantines, strips the message of suspicious files, makes coffee
and cleans the kitchen.

I am very pleased with it (can you tell?)

Steven Brendtro