MailTest
Most tools say DKIM failed. MailTest tells you why
MailTest launched on April 17, 2026 with 7 votes, #1,538 of 21,248 launches that month and more than 90% of that year's launches.
What it does
SPF ✅ DKIM ✅ DMARC ✅ — yet your emails still land in spam? Most tools just say "DKIM failed" without explaining WHY. MailTest goes deeper: 12 technical checks + actionable insights that show you exactly what's broken and how to fix it. Self-hosted, open source (after 100 users), built for developers who need real answers, not just red/green checkmarks. Try it free: 3 tests/day, no credit card.
Does a similar job
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DMARC Checker2024 · dmarcchecker.app · ▲70Verify your DMARC, DKIM, and SPF settings with our free checker. Prevent bad actors from impersonating your domain and improve email deliverability.
VaultSandbox – Test your real MailGun/SES/etc. integrationJan 2026 · vaultsandbox.com · ▲58I've spent the last few months working on something I wish I'd had years ago. I kept running into the same issue: CI green, production mail broken. TLS handshake failures, DKIM alignment mismatches, SPF soft-fails ... the stuff that only surfaces when real mail servers are involved. Most test tools (Mailpit, MailHog) are catch-alls. They confirm "an email was sent" but don't validate the protocol. They also aren't designed for network-exposed environments: no auth, unprotected Web UI, easy to enumerate messages. VaultSandbox is my attempt at fixing that. It's a self-hosted SMTP gateway…
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