No it doesn't. And its unfortunate that solving the problem is a problem in itself. ;)
Changing email protocol would be a monumental task. That's like trying to get people to validate their code, it just won't happen until they are forced to do it, and that isn't going to happen either.
I believe we are stuck with SMTP for at least a few more years. In the mean time, we need to work with the existing protocols and implement the various suggestions to help minimize the impact of UBE, UCE, etc.
Here's the problem in itself; getting people to adopt the protocols.
A little OT, that whole challenge response protocol sure didn't go anywhere, huh? I get those Earthlink notifications and they go right into the bin. Same goes for SpamArrest.