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Glossary · Email authentication

DMARC

A DNS record that tells receiving servers what to do with mail that fails authentication for your domain, and where to send reports about it.

DMARC ties SPF and DKIM to the From address a person actually sees. A message passes DMARC when SPF or DKIM passes and the domain it passed for matches the From domain; this match is called alignment. The record is a TXT record at _dmarc.yourdomain.com starting with v=DMARC1, and its p= tag asks receivers to do nothing (none), to treat failing mail as suspicious (quarantine) or to refuse it (reject). The rua tag names an address for daily aggregate reports.

The usual path is to start with p=none and a report address, read the reports until they show only your own senders, then move to quarantine and finally reject. Large mailbox providers now expect a DMARC record from anyone sending in volume: Gmail and Microsoft ask senders of more than 5,000 messages a day for one, and p=none is accepted.

Sources: RFC 9989 (DMARC; obsoletes RFC 7489) (rfc-editor.org, checked oct 22, 2026); Gmail email sender guidelines (support.google.com, checked oct 22, 2026); Microsoft: Outlook requirements for high-volume senders (April 2025) (techcommunity.microsoft.com, checked oct 22, 2026).

Related terms

  • SPFA DNS record that lists which servers may send email for your domain, so receivers can reject mail from anywhere else.
  • DKIM (DomainKeys Identified Mail)A digital signature added to each email, checked against a public key in your DNS, that proves the message came from your domain and was not altered.
  • BIMIBrand Indicators for Message Identification: a DNS record that lets supporting inboxes show your logo next to authenticated mail.
  • DeliverabilityHow reliably your emails reach the recipient's inbox, rather than being rejected, filtered to spam or delayed.

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