DMARC
also: Domain-based Message Authentication, Reporting and Conformance
DMARC (Domain-based Message Authentication, Reporting and Conformance) is an email authentication standard that uses SPF and DKIM to verify that messages claiming to be from a domain actually come from that domain's authorized servers.
DMARC is a protocol that allows domain owners to publish policies about how mail servers should handle messages that fail authentication checks. It works by examining SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) records to verify the message authenticity.
A DMARC policy is published as a DNS TXT record (e.g., _dmarc.example.com) and specifies what action to take for failed messages: none (monitor only), quarantine (mark as spam), or reject (refuse delivery). For example: v=DMARC1; p=reject; rua=mailto:[email protected]
DMARC also generates aggregate and forensic reports sent to specified email addresses, allowing administrators to monitor authentication failures and detect spoofing attempts. This helps prevent phishing attacks where criminals impersonate legitimate domains.