Authentication
DMARC
Domain-based Message Authentication, Reporting & Conformance. A policy framework building on SPF and DKIM.
Definition
DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication protocol that builds on SPF and DKIM. It allows domain owners to specify how receivers should handle emails that fail authentication checks (none, quarantine, or reject) and provides reporting mechanisms. DMARC prevents domain spoofing and phishing by ensuring only authorized senders can use your domain.
Examples
v=DMARC1; p=reject; rua=mailto:dmarc@example.com - Reject all unauthenticated emails and send reports
Pro Tip
Start with p=none to monitor, then move to p=quarantine, and finally p=reject as you fix authentication issues.