DMARC Ties Mail Authentication to the Visible From Domain
Email can carry several domain identities at once. The address displayed in the From header can differ from the envelope sender used by SMTP, while a DKIM signature can name yet another domain in its d= tag. SPF and DKIM authenticate identities from those separate protocol layers; neither mechanism alone requires its authenticated domain to match the domain presented to a recipient in From. Domain-based Message Authentication, Reporting, and Conformance (DMARC), specified in RFC 7489, connects those layers. A receiver evaluates SPF and DKIM, tests domain alignment against the RFC5322.From domain, and obtains a policy published by that domain. A message passes DMARC when at least one qualifying SPF or DKIM path both authenticates successfully and aligns.