SMTP ain't dead, it just smells funny.
There is a simple way to make spam a thing of the past. It only requires two things;
WARNING!
The quality of DNS-based and other blacklists varies a lot!
DUL-lists for instance, are supposed to list dynamic IP addresses, but
often list static IP addresses as being dynamic. So it's best not to use
DUL-lists.
Some lists publish entire /24's instead of individual IP addresses. Don't
use these blacklists either (it is OK to list entire IPv6 /64's though).
Some lists delist automatically. Others require manual delisting. The
latter will result in more false positives.
See;
Comparison
of DNS blacklists
Al Iverson's DNSBL Resource
Fighting non email spam.
These may include snail mail spam, sneaker spam (sales / market droids calling
at your door), phone spam (telemarketing) and horizon spam (over the top billboards).