Spam filters weigh many signals, and no outsider can see all of them. Email authentication is the part you can check directly, because it is published in your DNS.
SPF lists the servers that may send for your domain. If a newsletter tool or contact form sends from a server that is not on the list, receivers may treat the message as suspicious.
DKIM adds a signature that receivers check against a public key in your DNS. Missing signing, a wrong selector or a changed key makes the check fail.
DMARC ties SPF and DKIM to the address people see in the From line. Some large receivers expect it, especially from bulk senders.
Content, sending history and recipient behaviour also count. Fixing authentication removes one common cause, but it does not guarantee delivery.
DNS Domain Detective checks SPF, DKIM, DMARC and MX together and lists the exact records to fix. Open DNS Domain Detective
DNS Domain Detective is now available on the App Store.
Last reviewed: 2026-11-02
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This page gives general information and is not legal, financial or medical advice. [email protected]