Koltrix
Free tool
SPF, DKIM and DMARC, checked in one go.
Paste a domain and find out whether the three records that decide if your email arrives are published, valid, and set to something useful. No signup, nothing stored.
What this checks
- SPF — that exactly one record exists, that it ends in a sensible
allmechanism, and that it stays within the 10-lookup limit. - DKIM — that a public key is published at your selector and has not been revoked.
- DMARC — that a policy record exists, what the policy is, and whether reports are being collected.
- MX — where mail for the domain is delivered, and whether there is a fallback.
- Koltrix setup — for a domain on Koltrix, that its records are in place (ownership, MX, the
_spf.koltrix.cominclude and the domain’s own DKIM key), and whether an older setup has an upgrade waiting.
Questions about the checker
Why does the DKIM check say missing when I know I have DKIM?
DKIM keys are published under a selector name that you or your provider choose, and there is no way to list them from outside. We try 11 common selector names (Koltrix's kx1 first); if yours is not one of them, enter it in the selector box and we will check it directly.
Is this the same as being on a blocklist?
No. These three records are about authentication — proving a message really came from your domain. Blocklists are about reputation. We do not offer a blocklist checker, because the major blocklists refuse queries from shared infrastructure and would give you an answer that looks clean but is not.
Do you store the domains people check?
No. The lookup runs, the page renders, and nothing is written down.
Tired of doing this by hand?
Koltrix generates these records for your domain and checks them live while you set it up. 7 days free, no card.
More free tools: all of them · SPF, DKIM and DMARC explained