By the team at MailTester Ninja, a real-time email verification API that stores nothing.
We resolved the MX records of 50,000 of the most-linked domains (80.7% are mail-enabled) and classified who actually receives their mail:
- Other / self-hosted, 32.5%
- Google Workspace / Gmail, 28.2%
- Microsoft 365 / Outlook, 22.7%
- Proofpoint, 5.6%
- Mimecast, 3.1%
- Tencent QQ, 2%
- Namecheap, 1.2%
- Cisco IronPort, 0.9%
Google Workspace (28.2%) and Microsoft 365 (22.7%) anchor the market, but "Other / self-hosted" stays huge. That long tail is exactly why deliverability is hard: every provider greylists, rate-limits and reputation-scores differently. A sender that sails into Gmail can be throttled by a self-hosted Postfix or a Proofpoint gateway. Testing against real MX behavior, not assumptions, is the only way to know an address is actually reachable.
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, 10 Aug 2026 04:18:49 GMT.
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