← All insights · Thu, 02 Jul 2026

Who actually enforces DMARC? Reject rates by email provider

Enforcement isn't uniform — where a domain is hosted predicts whether it's protected.

DMARC enforcement isn't spread evenly — it tracks who hosts the mail. Share of each provider's domains that reach p=reject (and SPF -all):

Other / self-hosted — 18.4% on p=reject, 41.8% on SPF -all
Google Workspace / Gmail — 26.8% on p=reject, 25.9% on SPF -all
Microsoft 365 / Outlook — 31% on p=reject, 60.8% on SPF -all
Proofpoint — 61.5% on p=reject, 44.2% on SPF -all
Mimecast — 35.4% on p=reject, 42% on SPF -all
Tencent QQ — 2.4% on p=reject, 6.4% on SPF -all
Namecheap — 1% on p=reject, 1.2% on SPF -all

Proofpoint leads on enforcement (61.5% reject). Managed security gateways pull their customers toward strict policy by default, while self-hosted / other lags (18.4% reject) — enforcement is a config someone has to choose, and manageds choose it for you. The practical read: the reputation and policy of an address depends heavily on its provider, which is exactly why testing against the real receiving server beats guessing from the domain alone.

Verify a real address → This is aggregate DNS data. To check whether a specific email address exists and is deliverable, use MailTester Ninja — real-time, nothing stored.

Data: MailTester Ninja Email Infrastructure Index — 50,000 domains, snapshot Thu, 02 Jul 2026 08:16:19 GMT. Reuse freely under CC BY 4.0.

FAQ

Which email provider enforces DMARC the most?

In this sample, Proofpoint has the highest p=reject rate at 61.5% of its hosted domains.

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