Postfix

About DKIM

DKIM is an Internet Standard that enables a person or organization to associate a domain name with an email message, as such, claiming responsibility for the message. At its core, DKIM is powered by asymmetric cryptography. The sender's Mail Transfer Agent (MTA) signs every outgoing message with a private key. The recipient retrieves the public key from the sender's DNS records and verifies if the message body and some of the header fields were not altered since the message signing took place.