RFC 4871, DomainKeys Identified Mail (DKIM), defines a domain-level authentication framework for email using public-key cryptography and key server technology to permit verification of the source and contents of messages by either Mail Transport Agents (MTAs) or Mail User Agents (MUAs). . This is a Perl implementation created by Jason Long of Messiah College. It performs signing as well as signature verification. It also supports the older DomainKeys standard.