Free tool

SPF, DKIM and DMARC checker

Enter the domain your emails come from. The checker reads its SPF, DKIM, DMARC and MX records and tells you what will make receivers reject or spam-folder your mail. It runs in your browser.

What each record does

SPF lists the servers allowed to send for a domain. Receivers check it against the domain in the envelope sender (the Return-Path of a delivered email).

DKIM publishes a public key at selector._domainkey.domain. Your provider signs each email with the private key, and receivers verify the signature with this key.

DMARC at _dmarc.domain tells receivers what to do when an email fails both SPF and DKIM for a domain that matches its From address, and where to send reports.

MX records say which servers receive mail for the domain. They don't affect sending, but a sending domain without them can't receive bounces or replies.

Staging often sends from a domain nobody set up. Why emails from staging land in spam walks through the usual causes.

Questions

Why didn't it find my DKIM key?
DNS has no way to list DKIM selectors, so the checker tries the ones common providers use. Find yours in the s= tag of the DKIM-Signature header of an email you sent (the header analyzer shows it) and enter it in the selector field.
What does the 10-lookup limit mean?
Evaluating SPF may cause at most 10 DNS lookups, counting every include, a, mx, ptr, exists and redirect, including those inside included records. Above 10, SPF fails for every message (RFC 7208, 4.6.4). Each email provider you add usually costs one or more.
Is p=none enough?
It is the right first step: you get reports without affecting delivery. It doesn't stop anyone from sending as your domain. Move to quarantine, then reject, once the reports show only your own senders.
Where do the lookups go?
From your browser to Cloudflare's public DNS resolver over HTTPS, or to Google Public DNS if Cloudflare doesn't answer. Zyntra's servers are not involved and don't see the domain.

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