Good luck!
There are loads of these databases for sale. They collect addresses from Usenet and web pages, with trojans and spyware from people's address books and chain letter headers.

This is why I hate non-blind cc mass mailings. ONE PERSON on the list can get infected and everybody in their address book winds up on one of these lists, and everybody in the message header when that message gets mined. I've been on those spam lists before. You can't really do anything about it since the list has been copied and spread all over the place already.

Change e-mail addresses and protect the new one as if it were your house key.