This email protocol provides a mechanism for email senders and receivers to determine whether or not a given message is legitimately from the sender, and what to do if it isn't. It relies on the results of checking the messages against the policies defined in the Sender Policy Framework and DomainKeys Identified Mail records.
DomainKeys Identified Mail (DKIM)
Security Policy Framework (SPF)
Protected Domain Marks Recording (PDMR)
Domain-based Message Authentication, Reporting and Conformance (DMARC)