You can view the headers of the offending email message to aide in determining the origin of the email/virus. Most of the time, these viruses spoof the origin or transmit themselves from the actual infected machine, thereby bypassing the need for a smtp server to launch themselves on (they use the infected host for smtp).
The 'snoopy' virus that I have read about is pretty rare and has a payload for Linux users. Many Linux users don't run virus software, despite the continuing growth of viruses for this platform. If I am not mistaken, the 'snoopy' virus would need to come from a Linux infected host machine and could only come from the PC/Windows via somebody spreading this virus manually. Since I have not encountered this particular virus, I am not sure of the symptoms of an infected machine, the payload, or how it spreads itself.
We should always thank ourselves for having up to date virus protection. They sure have saved many possible issues. Too bad they couldn't stop the SQL Server 2000 virus a few weeks back, that one had the majority of my T3 line tied up with network traffic generated.
I have been sent the Snoopy Virus twice from the forum Beware.
It came as <greybeard>@greybeardoutdoors Or something close
norton caught it and quaratined it.
Tom