Microsoft is suggesting a new tactic in the fight against spam. Execs have proposed a broad industry plan to publish technical details about big companies' email servers, in an attempt to block fake email.
Differential filtering based on reputation management of an authenticated sending service. I proposed this in usenet posts over two years ago and on my spam page. I suspect someone else proposed it about 8 years ago.
This will work. It doesn't require Palladium. It doesn't require all of us to have a Passport or manage personal keys. It doesn't require ePostage or load metering. It's not fancy, it's not automatic, but it will work. It moves the user authentication problem to the sending service, which is where it belongs.
In big complex world, authentication and reputation are fundamental. With spam as with junk products as with brands -- it's a recurrent pattern.