The world of email viruses has changed. In the old days, they would piggyback on the messages you sent, or make your regular mail program send them out while you weren’t looking. These days they send the messages themselves, so they pick a fake return address from the same source as its list of victims: address books, web caches, and so on.
The return address on a virus like Sobig doesn’t mean crap.
So why the heck are all these idiotic virus scanners (*cough* Declude *cough*) sending me messages saying “You sent us a virus!” when a cursory glance at the headers clearly shows that it originated on the other side of the planet?
I’ve already got the server filtering out the virus itself – I’m seriously thinking about filtering out the useless warnings.