Here is a bit more information that may help you understand my problem. I run a site called www.colosource.com that is a free informational portal for the colocation industry. Periodically, a user sends a bunch of Spam to the listed email addresses.

Most Spammers I contact will say sorry, blah, blah, blah and stop but a few keep Spaming. The worst part of this is that the HTML code auto populates the subject line with :"Information request generated from www.colosource.com" as well as bcc me a copy.

So you see I end up with a valid return email address but a few buggers just will not stop, ruining the reputation of the service we provide.

HELP, HELP

<re-edited to kill run-ons>
Woops, didn't notice that. You have one of those "e-mail all the companies" type things? Make sure you record their IP. Also you may want to impliment some kind of signup requirement or an e-mail confirmation thing where a link is generated and sent to their e-mail address. Once they click it the request could be sent out. Could also make the script your using for this see if any key phrases the spammers are using have been submitted in the message and have it just act like it sent it but actually just scrap the request.