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Senddio glossary · Domain-based Message Authentication, Reporting and ConformanceLast reviewed: May 2026

What is DMARC?

DMARC (Domain-based Message Authentication, Reporting and Conformance) is an email policy standard. It sits on top of SPF and DKIM and tells receiving mail servers exactly what to do when a message claiming to be from your domain fails authentication.

How DMARC works in plain English

You publish a DMARC policy in DNS at _dmarc.yourdomain.com. The policy says one of three things: none (just monitor and report), quarantine (send to spam), or reject (refuse the message entirely). When a receiving server gets a message from your domain, it checks SPF and DKIM, and applies your DMARC policy to the result.

Why DMARC matters

Without DMARC, anyone can attempt to spoof your domain in their From address. With DMARC set to reject, receiving servers throw out impersonation attempts before they reach your customers. It is the strongest defence against phishing that uses your brand.

What does a DMARC record look like?

A DMARC TXT record at _dmarc.yourdomain.com looks like: v=DMARC1; p=reject; rua=mailto:dmarc-reports@yourdomain.com. The p= field is the policy. The rua= field tells receiving servers where to send aggregate failure reports.

Start gentle, then strengthen

Best practice is to start with p=none and monitor reports for a few weeks. Once you confirm that all your legitimate senders are passing SPF and DKIM, move to p=quarantine, then eventually p=reject. Jumping straight to reject can cause legitimate messages to be lost.

Related terms
DKIM SPF
FAQ

DMARC — FAQ

Yes, since 2024. Google and Yahoo require senders of more than 5,000 messages a day to have DMARC published, with at least a p=none policy. Microsoft has signalled similar requirements. Without DMARC, your messages will be heavily filtered.

p=none asks receivers to send you reports but take no action. p=quarantine asks receivers to deliver failing messages to spam. p=reject asks receivers to refuse failing messages outright. Most mature domains run on p=reject after a careful rollout.

Senddio generates a starter DMARC record (p=none) for every verified domain and shows you when to move to stricter policies. You publish the record in your own DNS so you keep full control of the policy.

Senddio handles the boring parts of DMARC for you.

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