Hello, I'm not sure if you are aware but SPF is doing something similar but a lot easier to setup : it tells all the servers to accept or deny an email depending on the server sending it. Unfortunately for SPF, just like your system, everyone is not using it. If every domain was using SFP properly, all webservers could simply block emails sent through unauthorized servers and that'd be it ! But people are just not concerned enough to setup SPF on all their domains and domains without SPF setup properly or just not setup are the ones used to send spam and succeeding ... So sad ... Have a nice day ! (and I'm not sure this mailing list is here to discuss enhancement to The Internet, there are other places to better do that, I'm sure) Frederic Vagner HaiSoft