DKIM

DKIM is an authentication technique that allows the recipient to verify whether an email message has actually been sent by the owner of the email domain. When sending emails, this email message is signed by the emailserver with a digital private key and then validated at the receiving mail server using a digital public key located in the public DNS. DKIM offers strong email security because DKIM signatures (unlike SPF) can survive the check on forwarding emails.

Check the current security of your domain: