Glossary · Security and privacy
DMARC
A DNS record telling receiving mail servers what to do with a message that claims your domain and fails authentication: none, quarantine or reject.
What DMARC means
A DNS record telling receiving mail servers what to do with a message that claims your domain and fails authentication: none, quarantine or reject. It evaluates SPF and DKIM results for alignment with the visible From domain; it authenticates nothing itself, and p=none is monitoring, not protection.
What DMARC can and cannot support
| It can support | It cannot support |
|---|---|
| A DNS record telling receiving mail servers what to do with a message that claims your domain and fails authentication: none, quarantine or reject. | It evaluates SPF and DKIM results for alignment with the visible From domain; it authenticates nothing itself, and p=none is monitoring, not protection. |
Where DMARC comes up on this site
- DMARC p=none to p=quarantine without losing mail: a guideA DMARC record with p=none is a monitoring instruction: it asks receiving mail servers to report what they see and to deliver everything anyway.
- Release notes 29 Sep 2026: finding states, sitemap, trustTrust center, terms, refunds /trust is built from the running configuration rather than written about it: the retention table reads the real TTLs (reports 90 days, leads 180, the comment queue 30, Search Console and Business Profile data 400, sessions 12…
Terms this definition uses
Definitions that name DMARC
Related terms in Security and privacy
Where an agent, a tool or a page can be turned against its operator, and the controls that limit the damage without proving safety.
Indirect prompt injection · Direct prompt injection · Jailbreak · Data exfiltration · Sensitive information disclosure · Secret leakage · Insecure output handling · Excessive agency · Least privilege · Trust boundary · Input validation · Output validation · Allowlist · Denylist · SSRF · RCE · Credential scope · OAuth scope · API key · Bearer token · mTLS · Rate-limit policy · Audit log · PII · Data minimization · Purpose limitation · Retention period · Data residency · Tenant isolation · Threat model · DMARC alignment · SPF · DKIM · MTA-STS · TLS-RPT · CAA record · DNSSEC · hard bounce
Questions about DMARC
What is DMARC?
A DNS record telling receiving mail servers what to do with a message that claims your domain and fails authentication: none, quarantine or reject.
What does DMARC not show or guarantee?
It evaluates SPF and DKIM results for alignment with the visible From domain; it authenticates nothing itself, and p=none is monitoring, not protection.
Which area of the glossary does DMARC belong to?
Security and privacy: Where an agent, a tool or a page can be turned against its operator, and the controls that limit the damage without proving safety.
← Threat model · DMARC alignment →
See it in the full glossary · 668 terms across 19 areas.