recognizing spam sent by viruses

[Rob McEwen <ro...@powerviewsystems.com>]

Is there some way of knowing for **sure** whether a spam which does NOT
actually contain a virus was sent by a virus?
 
Is there a corpus of such examples anywhere?
 
Also, do these viruses ever use the SMTP server set up on that computer in
Outlook (via Windows registry), or do they always use external third-party
smtp servers for sending the spam?
 
(I'm researching this as a prerequisite to trying some additional anti-spam
strategies.)
 
Thanks,
 
Rob McEwen