I thought it was pretty clear that he was talking about e-mail spam submitted using HTTP to webmail services like hotmail, yahoo and gmail:
I guess I'm still a little confused about the poster's original request. It sounds like he is interested in stopping his own users from spamming via web-based email services such as Gmail and Hotmail, or via insecure forms. That can be accomplished hypothetically by filtering HTTP requests and looking for spam in POSTs; although with the proliferation os AJAX-style interfaces in these services, figuring out which POSTs refer to a message submission is far more difficult than it was in the good old Web 1.0 days. Regards, Ken -- MailChannels: Reliable Email Delivery (TM) | http://mailchannels.com -- Suite 203, 910 Richards St. Vancouver, BC, V6B 3C1, Canada Direct: +1-604-729-1741