A DKIM selector is a label that tells receivers which public key to look up, at {selector}._domainkey.yourdomain.com. It lets one domain run several DKIM keys at once — one per sending service — and rotate keys without downtime. Find yours in the s= value of a message’s DKIM-Signature header.
A domain often sends through several platforms (Google, a CRM, a newsletter tool), each with its own key. The selector namespaces them: Google uses google, Microsoft 365 uses selector1/selector2, and ESPs use values like s1, k1 or mail. Selectors also let a provider rotate keys by publishing a new selector.
Open a message you sent, view the original/headers, and read the DKIM-Signature line: d= is your domain and s= is the selector. Then look up {s}._domainkey.{d} to see the published key.
Substitute your selector and domain:
$ dig TXT selector1._domainkey.yourdomain.com +shortCheck your DKIM record now
Open the free DKIM checker →Yes — that’s the point. Each sending service publishes its own selector and key under the same domain.
In the DKIM-Signature header, the s= tag is the selector and d= is the signing domain.
