The pct tag is an optional field in a DMARC record (RFC 7489) that sets the percentage of messages failing DMARC to which the requested policy is applied. It accepts a whole number from 0 to 100; the default when omitted is 100.
It exists to make moving to enforcement less risky. If you publish p=quarantine; pct=25, receivers apply quarantine to roughly a quarter of failing messages and treat the rest with the next lower policy (none for quarantine, quarantine for reject). This lets you watch aggregate reports for collateral damage before committing fully.
A common rollout is p=quarantine; pct=10, then 25, 50, 100, and finally p=reject. Note that pct is a sampling instruction only: it never changes alignment results, and not every receiver honours it consistently. A newer DMARC revision deprecates pct in favour of t= testing, but pct remains widely supported today.
Check the value with a DMARC lookup tool. A done-for-you service like DMARC Engine manages this ramp automatically, watching reports at each step so legitimate mail is never lost on the way to full enforcement.
Check it on your domain
- DMARC Checker: look up and validate a domain's DMARC record and policy.
- DMARC Generator: build a valid DMARC record from a simple form.
- DMARC Report Analyser: read a DMARC aggregate (RUA) report in plain English.