cryptographically identify the sender of email - perl library

 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.