MailCheck — Email Deliverability & DNS Checker
korpo.pro
Check SPF, DKIM, DMARC, MTA-STS, TLS-RPT, BIMI for any domain. Free, instant, no signup. Get a 0-100 deliverability score.

According to Talos Intelligence, about 20% of legitimate emails are never delivered. The #1 cause is misconfigured SPF/DKIM/DMARC records.

I built mailcheck — a free, open-source tool that audits 6 email authentication protocols in one pass:

  • 🔍 SPF — Sender Policy Framework (record validity, +all/~all/-all, DNS lookup limits)
  • 🔐 DKIM — DomainKeys Identified Mail (17 common selectors, key size validation)
  • 🛡️ DMARC — Domain-based Message Authentication (policy strength, reporting)
  • 🔒 MTA-STS — SMTP MTA Strict Transport Security (RFC 8461)
  • 📊 TLS-RPT — TLS Reporting (RFC 8460)
  • 🏷️ BIMI — Brand Indicators for Message Identification

Each domain gets a 0-100 deliverability score with plain-English fix recommendations.

Try it: https://korpo.pro/ — type any domain, get instant results.

Self-host: pip install mailcheck — MIT licensed, 73 tests, CI/CD friendly (exit code 2 on critical issues).

Source: https://korpo.pro/git/mailcheck/mailcheck