Pesky spammers are using my mailbox

Hi, seems some spammers are using one of my personal domains as the from field in their emails, the local-part being random so I cant easily block it. Has anyone any advice on tracking them down and making them stop? All I get are the bounces, some include the original headers but that usually gives an open relay as the origin. I think I know the answer (you cant do anything) but I wanted to ask as its very annoying and I'm not happy! PS Anyone around at the Sheraton today.. I cant spot anyone looking nanogish! Steve