Unfortunately that might not be the best plan of attack. Most of the time spammers don't have a valid reply address. This means your reply message will bounce back to you. They'll still send you more spam, which means you'll get double the messages. I'd recommend using a program like the following to fake a bounce reply to their mail server. (This just happens to be the first program I came across)
http://www.webattack.com/get/bounce.shtml
