What is Domain-based Message Authentication, Reporting & Conformance (DMARC)?
DMARC is an email authentication protocol that helps email marketers protect their domain from being used in phishing and spoofing attacks. It builds on two existing mechanisms, SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail), to provide a way for domain owners to publish their email authentication practices and specify how receiving mail servers should enforce them.