Yahoo proposes new Internet anti-spam structure: Good thing this is Yahoo!, because it’s going to take a big company to pull this off. They’re apparently going to open-source it.
Under Yahoo’s new architecture, a system sending an e-mail message would embed a secure, private key in a message header. The receiving system would check the Internet’s Domain Name System for the public key registered to the sending domain.
If the public key is able to decrypt the private key embedded in the message, then the e-mail is considered authentic and can be delivered. If not, then the message is assumed not to be an authentic one from the sender and is blocked.