Haven't we had this discussion at least twice. Marcus and others wrote
long messages detailing the problem of checking for a virus inside mail
messages - uuencoded messages, encrypted messages, uuencoded encrytped
messages, ... ad nauseum, but there isn't much point. If someone is
going to run a program they get in mail, then they will probably run a
program they ftp or http.
It is certainly possible to run some type of virus scanner that will
catch some, but it will only give a false sense of security.