← All insights · Thu, 02 Jul 2026

Who runs the world's inboxes? MX market share across 50,000 domains

Google, Microsoft, self-hosted — and a very long tail. Why deliverability is hard.

We resolved the MX records of 50,000 of the most-linked domains (80.6% are mail-enabled) and classified who actually receives their mail:

Other / self-hosted — 32.5%
Google Workspace / Gmail — 28.3%
Microsoft 365 / Outlook — 22.6%
Proofpoint — 5.5%
Mimecast — 3.1%
Tencent QQ — 2%
Namecheap — 1.2%
Cisco IronPort — 0.9%

Google Workspace (28.3%) and Microsoft 365 (22.6%) 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.

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

What is the most popular email provider?

In this sample, Google Workspace / Gmail leads at 28.3% of mail-enabled domains, followed by Microsoft 365 / Outlook at 22.6%.

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