IETF had a BOF discussing spam some years ago, but as I
remember all or most of what was said would not work simply
because spammers can find other ways around them.
Depends on your problem space. If your goal is to ameliorate spam from
the entire global Internet, you're right. Given the current state of
the Internet email infrastructure and the current probability that it's
likely to change any time soon, spam is here to stay.
However, RFC 2635 has a lot of good advice for how to keep spam off
your system. It is possible to almost eliminate spam from any one
server. The "almost" is because spam is in the eye's of the beholder;
one man's spam is another man's lunch.
In fact, I would assert that spammers are not getting smarter at all and
characterizing them as "finding other ways around" is giving them way
too much credit. The methods used by spammers haven't changed all that
much in the recent past (say, a year or more). The problem is the email
infrastructure as a whole offers more opportunity than challenge to
spammers. Sending spam is downright trivial and with the free tools
available you don't even have to understand it!
Jim