If they are emails, then there isn't much you can do to stop a deluge besides changing the email address. Any time someone's email address gets out, whether by using it in newsgroups, chat rooms, to buy something online, or by a "friend" using their address in a mass mailing of a forwarded message, the address becomes available to spammers and to other PCs that may be infected with viruses.
I have had email addresses that were sold to spammers by online merchants, and shortly became unusable due to the high volume of crap that I received. There are folks where I work that are getting dozens of virus emails a day, probably because of the above mentioned reasons.
We can filter quite a bit through the server, but the text of the virus messages still come through. (On a similar note, I would like to see every email server in the entire world *quit* responding to emails with viruses by sending warning emails to the alleged senders, especially since we know it almost certainly did not originate at that address.)