Domainkeys has the backing of Yahoo, Cisco Systems, Sendmail and PGP Corporation because it will provide "businesses with heightened brand protection by providing message authentication, verification and traceability to help determine whether a message is legitimate."
Basically it works by inserting a digital signature into the legitimate message which is checked. If it fails the ISPs can decide if they want the message flagged as junk. DomainKeys are good at identifying spoofed e-mail too.
It will probably work for the five minutes it takes for spammers to get a work around. More here. ยต