By the team at MailTester Ninja, a real-time email verification API that stores nothing.
We took every mail-enabled domain in the sample (those with MX) and walked them down the authentication funnel:
- Mail-enabled (have MX), 100%
- Publish SPF, 91.7%
- Publish DMARC, 77.6%
- Enforce (quarantine or reject), 48.9%
- Reject (p=reject), 26.7%
The story is the drop-off. Publishing SPF is nearly universal (91.7%) and DMARC adoption is high (77.6%), but only 48.9% enforce anything (quarantine or reject), and just 26.7% reach p=reject. Every step down that funnel is a domain that did the paperwork but left the door open. If you operate a domain, the win isn't publishing another record, it's moving one step down the funnel toward enforcement.
Check any domain yourself, MailTester Ninja's free deliverability tools cover it end to end in one place: MX / SPF / DMARC analysis, an inbox-placement test scored out of 100, an SPF & DMARC generator and a blocklist checker, all with no signup and nothing stored. Need to confirm whether a specific mailbox actually exists and is deliverable? That is exactly what MailTester Ninja's email verifier does in real time, and we store no data.
Source: MailTester Ninja's open Email Infrastructure Index, a live DNS scan of 50,000 of the world's most-linked domains, updated daily, aggregate only. Free to cite under CC BY 4.0. Snapshot: Mon, 31 Aug 2026 04:18:17 GMT.
