DMARC Checker
Find the DMARC policy published for any domain and read what it asks receivers to do.
What is a DMARC record?
DMARC (RFC 7489) builds on SPF and DKIM. It tells receivers what to do with mail that fails those checks, and where to send reports about it.
The record is a TXT record published at the "_dmarc" subdomain — for example, "_dmarc.example.com" — and starts with "v=DMARC1".
Policy and alignment
The "p=" tag carries the policy: "none" asks only for reporting, "quarantine" asks receivers to treat failing mail as suspicious, and "reject" asks them to refuse it outright. "sp=" sets a separate policy for subdomains.
DMARC passes when SPF or DKIM passes *and* the relevant domain aligns with the From header domain. The "aspf" and "adkim" tags choose whether alignment is relaxed (organisational domain matches) or strict (exact match).
Rolling out DMARC safely
Starting at "p=none" with a "rua=" reporting address collects data without affecting delivery. The reports show which senders are failing alignment, including legitimate ones you may have forgotten.
Moving to quarantine or reject before your legitimate senders align is the usual way to break your own mail. Fix alignment first, then tighten the policy.