With DKIM, which relies on public key cryptography, a digital signature is attached to outgoing email so recipients can verify that the message comes from its claimed source. The idea is to make it easier to eliminate spam or phishing emails with spoofed addresses by marking out legitimate messages. The specification merges two earlier proposals, Yahoo!'s DomainKeys technology and Cisco's Internet Identified Mail system.
Many companies have been involved in this effort, including Alt-N Technologies, AOL, EarthLink, IBM, Microsoft and VeriSign, as well as Cisco Systems and Yahoo! themselves. The companies believe that this is a big milestone for the email authentication efforts going on to try and stop the plague that is spam.