Introduction to DMARC and the p=quarantine Policy DMARC (Domain-based Message Authentication, Reporting, and Conformance), defined in RFC 7489 , is an email authentication protocol. It builds upon SPF and DKIM to provide domain owners with the ability to protect their domain from unauthorized use. DMARC enables senders to specify how receiving mail servers should handle unauthenticated emails originating from their domain. It also provides a mechanism for receiving servers to report back ...