Author Domain
DMARC's name for the domain in the message's From header, the address the reader sees and the domain whose policy DMARC applies.
What it means
RFC 9989 defines the Author Domain as the domain of the From header field (RFC5322.From). It is the anchor of DMARC: the policy is looked up for it, and SPF and DKIM only count when their authenticated domains align with it.
A message without exactly one valid From header cannot be evaluated, since there is no reliable domain to look up. Gmail rejects messages whose From header is missing or invalid, or names more than one sender.
The display name before the address plays no part. That leaves display-name spoofing, where the name shows a trusted brand over an unrelated address, outside what DMARC can stop.
Related terms
On this site
Sources
What this definition rests on. The wording is ours; the facts are theirs.
- RFC 9989: Domain-based Message Authentication, Reporting, and Conformance (DMARC), section 3.2.2rfc-editor.org
- RFC 9989: Domain-based Message Authentication, Reporting, and Conformance (DMARC), section 4.4rfc-editor.org
- RFC 9989: Domain-based Message Authentication, Reporting, and Conformance (DMARC), section 11.4rfc-editor.org
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