In my previous post, I noted that rustock had started sending us a whole pile of spam over the TLS protocol. The question now is why do it at all? I mentioned in my post that this is clever behavior and one of my readers posted in a comment “What makes this so clever?” The issue of authentication, reputation and security is one that comes round and round in the world of email. Why do we authenticate? And what does it buy you? There are plenty of reasons to send authenticated mail, here are three: It allows you to track abusive behavior. If an organization is sending outbound spam, then determining who is responsible for it allows that organization to track down who is sending it and shut them down. This, of course, presumes that organizations want to do the right thing. But if you are taking responsibility for the quality of what you send, then identification of your users is done using authentication. It allows you to combat fraud.