DKIM adds a digital signature to your outgoing email, and receiving servers check it against a public record in your DNS. That record sits under a selector name, and whoever set it up chose that name.
A selector can be named almost anything, such as a date, a word or a provider's label. There is no list to look it up in. You need the right name before you can see the record.
The selector is part of the DKIM-Signature header of an email you sent. Look for the part that starts with s=. That is the name to check.
Once you know the selector, the record is published at the selector name followed by ._domainkey and your domain. It should contain a public key. If it is missing, receiving servers cannot verify your signature.
DNS Domain Detective finds DKIM selectors for you and shows the exact records to fix. It checks CNAMEs, SPF, DMARC and MX in the same run.
Enter your domain in DNS Domain Detective and see which records are in place. Open DNS Domain Detective
DNS Domain Detective is now available on the App Store.
Last reviewed: 2026-11-02
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