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DMARC

published · September 13, 2026 · updated · October 8, 2026

DMARC (RFC 7489) is a DNS policy at _dmarc.<domain> telling receivers what to do with mail that fails SPF and DKIM alignment — none, quarantine or reject — and where to send reports.

DMARC, Domain-based Message Authentication, Reporting and Conformance, is the policy of RFC 7489 that a domain publishes as a TXT record at _dmarc.<domain> to tell receivers what to do with a message that fails both SPF and DKIM alignment with the visible sender — p=none to only report, p=quarantine to filter, p=reject to refuse — and where to send the aggregate reports that show who is sending as the domain.

What Spaw answers

Every email answer carries dmarc_policy; the domain endpoint adds dmarc_pct, the share of failing mail the policy applies to (100 when the tag is absent), and dmarc_rua, whether a reporting address is published. A reject or quarantine policy raises mailbox_confidence on a catch-all domain, because an administered domain is likelier to hold the mailbox than a squat; a relay alias is the exception, since the policy describes the relay operator, not the alias.

What it does not mean

A policy of none is a maintained domain that has not finished the rollout, not an unauthenticated one, and a reject policy says nothing about whether a particular mailbox exists. DMARC is about who may use the name, never about who reads the mail.

Related

markdown version: /glossary/dmarc.md

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