Check the mail setup of all your domains at once
Paste up to 25 domains, one per line. We check MX, SPF, DKIM, DMARC, the mail server's certificate and the main blacklists, then tell you what to fix.
OK Worth fixing Broken Could not tell. Click a row for the records and the fix.
How to test email deliverability without sending a single email
Most deliverability problems are visible in DNS before the first message goes out. Receivers like Gmail and Outlook look up the same records this checker reads, and they decide in milliseconds whether your mail is trusted.
| Check | What we read | Red when |
|---|---|---|
| MX | MX records of the domain | No MX, or MX points to a forwarding service only |
| SPF | TXT record starting with v=spf1 | Missing, two SPF records, more than 10 DNS lookups, +all |
| DKIM | TXT at common selectors, or yours | No key found, key under 1024 bit |
| DMARC | TXT at _dmarc | Missing or invalid; p=none is amber |
| TLS | Certificate on port 25 via STARTTLS | Expired, expires in under 14 days, wrong hostname |
| Blacklists | Mail server IPs on Spamhaus ZEN, SpamCop, Barracuda | Listed |
| PTR | Reverse DNS of the mail server IP | Missing or does not match |
Bulk check: why 25 domains at once
If you run many sites, each with its own contact@, one broken record hides among dozens of healthy ones. Paste the whole list, sort worst first, and fix from the top. Every red cell comes with a one-line fix and, where it helps, the exact record to copy into your DNS.
Read the guide to running email on many domains for the setup that keeps all of them at grade A.
Questions
How do I test my email deliverability for free?
Paste your domains above and press Check domains. In under 10 seconds you get MX, SPF, DKIM, DMARC, the mail server certificate, reverse DNS and blacklist status for each domain, with a grade from A to F.
Do I need to send a test email?
No. Everything is read from public DNS and from the certificate your mail server shows on port 25. That is why the check can run 25 domains at once.
What do the grades mean?
A: SPF, DKIM and DMARC with quarantine or reject, valid TLS, not listed. B: the same with DMARC p=none. C: one of SPF, DKIM or DMARC missing. D: two missing, or the certificate expires within 14 days. F: no MX, an expired certificate, or a blacklist listing.
Why is DKIM red when I know it is set up?
DKIM keys live under a selector name that only your mail host knows. We try the common ones (default, dkim, google, selector1, selector2, k1, mail, s1). Enter your selector in the field above and run the check again.
Do you store my domains?
No. Results are cached for one hour so repeat checks are fast, then dropped. Domains are stored only if you ask us to watch them weekly.
How often can I run it?
Up to 10 runs per hour, 25 domains per run. For more, use the weekly monitoring or the MXDeck app.
More free tools: DMARC checker · SPF checker · DKIM checker · MX lookup
Run 10, 30 or 100 domains?
MXDeck is a Mac email app with this check built in: one inbox for every contact@, and a red dot the day a domain’s mail breaks.