I started working on Petmail about 6 months ago to provide a technical
 alternative to the anti-spam "solutions" being proposed back then, proposals
 which, in my mind, either didn't solve the real problems or tried to solve
 the wrong problems. I think it is a good idea and the only "real" solution,
 but I don't pretend that the world is going to rush out and switch to Petmail
 overnight. My goal here today is not to convince you that Petmail will be
 your next mail system, but rather to convince you that your next mail system
 should offer all the features that Petmail provides, and that you should not
 be content with an anti-spam solution that provides less.