Source: Forbes

According to Microsoft, up to 90% of e-mail is spam. The company is one of a few key players to offer tantalizing peeks at technology intended to prevent spam from ever reaching users. Unfortunately, as one test case shows, competing technologies and ever-smarter scammers prevent the solutions from really fixing the problem.
This will be a battle that will be fought for a long time. The smarter we get at stopping the spam, the smarter they get at finding a way to beat the system.

Yahoo! and Cisco Systems are collaborating on an authentication technology to weed spam from legitimate e-mail. It goes by the clunky name DomainKeys Identified Mail (DKIM), and it merges technology from both companies into one specification based on public key cryptography, a type of digital signature. The companies submitted their blended solution to an Internet standards group, the Internet Engineering Task Force (IETF), which is studying e-mail verification.

Yahoo! is not alone. Microsoft has its own specification called Sender ID. Unlike DKIM, which digitally signs every message, SenderID examines the domain from which the message originated and checks whether it's coming from an authorized server. An IETF working group on SenderID expired last year, but Microsoft has continued its promotion.
Unless the all the key players can come up with a common solution, I don't see any of the above technolgies making it. With different standards, it will make it hard for any company to make sure they are supporting each type in order to make sure email is flowing like it was intended.