I would summize that your old ISP has a virus, and is sending everyone who ever sent or received an email, these messages on each of their accounts. If you ran an up-to-date virus scan; the chances are that the fault is not with you.
However, one question remains .... "are you on broadband?", and if so, "Are you using a Router?"
I have indicated this in the past, and will do so again for your benefit. One cannot over-emphasize the importance of purchasing a $30 Router from Wal-Mart if you are using Broad band.
What does the router do for you? I recently switched to bb