What is DomainKeys Identified Mail (DKIM) ?

DomainKeys Identified Mail (DKIM) lets an organization take responsibility for a message that is in transit. The organization is a handler of the message, either as its originator or as an intermediary. Their reputation is the basis for evaluating whether to trust the message for further handling, such as delivery. Technically DKIM provides a method for validating a domain name identity that is associated with a message through cryptographic authentication.
DKIM attaches a new domain name identifier to a message and uses cryptographic techniques to validate authorization for its presence. The identifier is independent of any other identifier in the message, such in the author’s From: field.

Introduction

The first version of DKIM synthesized and enhanced Yahoo!’s DomanKeys and Cisco’s Identified Internet Mail specifications. It was the result of a year-long collaboration among numerous industry players, during 2005, to develop an open-standard e-mail authentication specification. Participants included Alt-N Technologies, AOL, Brandenburg InternetWorking, Cisco, EarthLink, IBM, Microsoft, PGP Corporation, Sendmail, StrongMail Systems, Tumbleweed, VeriSign and Yahoo!. The team produced the initial specification and several implementations. It then submitted the work to the IETF for further enhancement and formal standardization.