There have been attempts at Secure-SMTP but some of them have issues with legacy and non-Windows OSes. One of the things, contrary to Bill's claim, is that much of the "phishing", spamming and other techniques will always work because they aren't dependent on technology to solve them. They are, however, dependent on humans to believe them. As long as humans believe the message they receive is legit there will be a market for this kind of abuse.