Mailcheck – Free/open-source email deliverability checker (SPF, DKIM, DMARC, MTA-STS, TLS-RPT, BIMI) (korpo.pro)

submitted 5 months ago by mailcheck@lemmy.dbzer0.com to c/selfhosted@lemmy.world

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Hey fellow self-horders!

I built mailcheck — a free, open-source tool that checks all 6 email authentication protocols (SPF, DKIM, DMARC, MTA-STS, TLS-RPT, BIMI) for any domain and gives you a 0–100 deliverability score.

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

Self-host it: It's MIT licensed with a FastAPI backend. pip install mailcheck or clone from our Forgejo repo.

CLI: mailcheck example.com — great for CI/CD integration (exit code 2 on critical issues).

API: curl https://korpo.pro/api/v1/check/example.com — no auth needed, 100 req/hr.

Batch mode: mailcheck --file domains.txt

I found that many well-known domains have misconfigurations — even big crypto projects. The tool helped me fix my own domain's email auth setup.

Would love feedback from email/infra folks!

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[-] irmadlad@lemmy.world 2 points 5 months ago

Firefox 149.0.2 (64-bit), Linux Mint, using VPN. I must have settings that are blocking the processing of the domain for whatever reason. I've tried multiple domains including well known domains. No joy. Sorry about that.

this post was submitted on 26 Apr 2026

39 points (91.5% liked)

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