How to alleviate spam, a simple perspective
It seems to me like the easiest way to get rid of SPAM would be to have mailservers check to see if the IP address of the e-mail sender resolves to the domain references in the “From” field. This would require people like me to register their home computers in their business DNS system when sending business mail, but so what?
Case in point, I just got one of those damned fake Microsoft alerts again. This time it went to my “Microsoft Correspondence” folder, because Outlook saw that it was from “updates.microsoft.com”. It OBVIOUSLY wasn't from that domain name, because the e-mail is a poor forgery at best. But if all e-mail servers tested IP resolution, it would be a lot harder to spoof the domain name, cause you'd have to spoof the IP too. It would take more effort to try to break through.
Just my opinion.