I think we have all agreed in previous threads that if a mail anti virus scanner does not know how to differentiate between a virus that spoofs the sender and one that doesnt, it should silently discard all virus infected email -- OR notify the local administrator/user at their choosing, but NOT bounce it.
Since the notion not to bounce a "you mailed a virus" message back the sender is heard everywhere, I thought I'd mention this.... Our mail server generates an incredible amount of bounces because of user accounts either not existing or being over quota. The signature based virus scanner hooks in at the local delivery, so the mail spool isn't scanned for viruses. As a result many messages are returned intakt, including attached virus, to the fake 'From:' address..... The fun and games of an archaic, abused, defunct mail delivery system... Adi