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What Is a DKIM Selector and a DKIM Key?

This article explains DKIM Selectors and DKIM Keys.

A DKIM selector is an essential part of your DKIM record, as you can generate and use multiple selectors to create unique DKIM keys for your domain. A selector is basically a keyword or an ID or a string that gives a DKIM key its uniqueness.

A DKIM key is created by appending the selector to your sending domain. So, if your domain is example.com and your selector is mail1, you create a DKIM key by appending them to a ._domainkey.. Here is this example's key:

mail1._domainkey.example.com

This DKIM key will then point to a published DKIM record at your DNS provider. When an email is sent, the sending email server utilizes it to retrieve the private key used to sign an outgoing message. Your DKIM selector also forms part of the email headers used by recipient servers to locate the domain’s public keys that help decrypt the email’s DKIM signature.

If you use a third-party provider to send email, your messages are likely DKIM signed. To ensure that your emails are DKIM signed, as well as to find the DKIM selector associated with them, see the following Gmail example.

How to Find a DKIM Selector/Key in an Email

  1. Send an email to your email address.
  2. Open the received email.
  3. From the More icon (three vertical dots), navigate to Show Original from the drop-down menu.
  4. Scroll down to the DKIM-Signature section. The tag s= is the selector.

Be sure to use our How to Get Email Headers: An MxToolbox Guide for step-by-step instructions regarding various email providers. Also, to make the corresponding email headers human readable, try MxToolbox's free Email Header Anaylzer.

For more information about DKIM Configuration and Key Monitoring, click here.