mailtester .eu
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How it works

From “send” to score, in three steps

MailTester follows the real path of an email: it receives your message like an actual mail server, analyzes it with the same criteria as major providers, and returns a transparent score.

1. Real SMTP reception

When you send your message to the test address, a Rust SMTP server actually receives it: it records the connecting IP, the HELO/EHLO, the envelope MAIL FROM and the full content — the same data the recipient's mailbox sees.

2. Authentication: SPF, DKIM, DMARC

We verify SPF against the sending IP, the DKIM signature over the message body, and DMARC alignment with the visible sender domain. We also check reverse DNS (PTR) and whether it is forward-confirmed.

3. Blacklists, content and spam engine

The IP is checked against the main DNS blocklists (Spamhaus, SpamCop, Barracuda and others). Content is analyzed for HTML, text/image ratio, links, subject, List-Unsubscribe and Message-ID headers. Finally the message goes through Rspamd, which assigns a spam score with the list of triggered rules.

The /10 score

We start at 10 and subtract points for each issue, weighting the factors that truly affect deliverability. Every penalty is explained and tied to a concrete fix — no number handed down from above.

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