SuperMailOS
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One grade for your domain's email health.

Authentication, mail routing, blocklists and domain age, checked together and graded A to F, with the specific fix for anything that's dragging the score down.

01 What goes into the grade

Four things decide where your mail lands.

Each check is worth the same. A pass counts in full, a warning counts half, a failure counts nothing, so the grade only reaches the top when nothing needs attention.

Authentication

SPF (including its 10-lookup limit), DKIM and DMARC. Receivers check these on every message; failing them is the fastest way into spam or a rejection.

Mail routing

MX records, so mail to you arrives at all, and MTA-STS, which forces the servers sending to you to use encryption.

Reputation

Whether the servers that handle the domain's mail appear on public blocklists that receivers consult before they even look at content. The blocklist checker links to the lists that don't allow public lookups.

Domain age

New domains carry no reputation, and most phishing comes from them, so receivers give young domains less benefit of the doubt.

02 Questions

Common questions.

Something else? Write to us — a real person answers, usually the same day.

Talk to us
How is the email health score calculated?+
We run seven checks: SPF (analysed in full, including its lookup limit), DKIM, DMARC, MX, MTA-STS, blocklists and domain age. Each is worth the same share of 100. A pass counts fully, a warning half, a failure nothing. Grades: A is 90 and up, B 80, C 65, D 50, F below that.
Does a good grade guarantee inbox placement?+
No tool can promise that. Gmail and Outlook also weigh how recipients engage with your mail and your sending history, which no DNS check can see. A good grade means nothing in your setup is working against you.
Why does my domain age lower the score?+
Because receivers treat it as a signal. A domain registered in the last few weeks has no track record, and it's what most throwaway phishing uses. It improves on its own with time and steady, wanted mail.
How often should I check?+
After any DNS change, after adding a new sending service (a newsletter tool, a CRM), and whenever replies suddenly dry up. A record edited for one tool often breaks another.

03 More free tools

Keep checking.

Each tool answers one question about a domain's email. All free, no signup.

All free tools ▶
Authentication→

Email deliverability checker

SPF, DKIM, DMARC, MX and MTA-STS in one pass, with a score and the fix for anything that fails.

Reputation→

Blocklist checker

An IP, or a domain plus its mail servers, checked against public DNS blocklists.

DNS & domains→

Domain age checker

Registration date, expiry and registrar from official RDAP data, and what age means for mail.

Get an A and keep it.

Every domain you run in one inbox, from $3 a mailbox. 14 days free, no card.

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