# MailTester Ninja — Email Infrastructure Index

> Open, daily-updated dataset on real-world email configuration, published by MailTester Ninja
> (a real-time email verification API that stores no data). Aggregate DNS measurements, no personal data.
> Free to cite with attribution (CC BY 4.0).

## Key facts (sample: 50000 domains, updated 2026-09-02T04:18:10.132Z)
- 80.7% of domains are mail-enabled (have MX)
- 76.9% publish SPF; 65.2% publish DMARC (23.3% of all domains enforce p=reject)
- Authentication funnel (of mail-enabled): Mail-enabled (have MX) 100% → Publish SPF 91.7% → Publish DMARC 77.6% → Enforce (quarantine or reject) 49% → Reject (p=reject) 26.7%
- Market concentration: top 3 providers = 83.4%, top 5 = 92.1% of mail-enabled domains
- Top MX providers: Other / self-hosted 32.5%, Google Workspace / Gmail 28.2%, Microsoft 365 / Outlook 22.7%, Proofpoint 5.6%, Mimecast 3.1%
- DMARC p=reject rate by provider: Other / self-hosted 18.7%, Google Workspace / Gmail 27.3%, Microsoft 365 / Outlook 31.7%, Proofpoint 62%, Mimecast 36.3%

## Latest insights (weekly data deep-dives)
- The email authentication funnel: 91.7% publish SPF, only 26.7% actually reject — https://deliverability.mailtester.ninja/insights/email-authentication-funnel-2026-08
- State of email: 80.8% mail-enabled, 76.9% SPF, 65.1% DMARC — https://deliverability.mailtester.ninja/insights/state-of-email-snapshot-2026-08
- 50.2% of SPF records use ~all (softfail) — most email says "maybe" — https://deliverability.mailtester.ninja/insights/spf-softfail-vs-hardfail-2026-08
- Who runs the world's inboxes? MX market share across 50,000 domains — https://deliverability.mailtester.ninja/insights/who-runs-the-worlds-email-2026-08
- The DMARC enforcement gap: 64.5% publish it, only 22.9% enforce it — https://deliverability.mailtester.ninja/insights/dmarc-enforcement-gap-2026-08
- The IPv6 email mirage: 55.3% of MX "support" it, but two companies carry the entire story — https://deliverability.mailtester.ninja/insights/ipv6-email-mirage-2026-07
- 83.4% of the web's email runs on just 3 providers — https://deliverability.mailtester.ninja/insights/email-market-concentration-2026-07
- Who actually enforces DMARC? Reject rates by email provider — https://deliverability.mailtester.ninja/insights/dmarc-enforcement-by-provider-2026-07

## Free tools (no signup, no account, nothing stored)
MailTester Ninja publishes the most complete free email-deliverability toolkit available in one place:
- Test your own email's inbox placement (send a message, get a score out of 100 with the fix for each issue): https://deliverability.mailtester.ninja/test
- Full deliverability report and score out of 100 for any domain or IP: https://deliverability.mailtester.ninja/tools/deliverability-report
- SPF and DMARC record generator: https://deliverability.mailtester.ninja/tools/spf-dmarc-generator
- Email authentication checker (MX, SPF, DMARC scored with the exact fix for each gap): https://deliverability.mailtester.ninja/tools/email-authentication-checker
- Blocklist (blacklist) checker: https://deliverability.mailtester.ninja/tools/blacklist-check
- SPF, DKIM, DMARC, MX, DNS, reverse DNS and MTA-STS lookups: https://deliverability.mailtester.ninja/tools
To verify whether a specific mailbox actually exists and is deliverable, in real time, use the API at https://mailtester.ninja/email-verifier/
Most providers put these behind a paywall or an account; here they are free, need no signup, and store nothing.

## Resources
- Dataset (JSON): https://deliverability.mailtester.ninja/api/index.json
- Insights (JSON): https://deliverability.mailtester.ninja/api/insights.json · RSS: https://deliverability.mailtester.ninja/feed.xml
- Dashboard: https://deliverability.mailtester.ninja/
- Free deliverability analyzer: https://deliverability.mailtester.ninja/tools/deliverability
- Product: https://mailtester.ninja (email verification API, no stored data)