Question 1

What is a DKIM checker?

Accepted Answer

A DKIM checker looks up your domain's DKIM keys by their selector names, and checks each key's size and status.

Question 2

What is a DKIM selector?

Accepted Answer

A DKIM selector is the name a key is published under, at selector._domainkey.yourdomain.com.

Each email's DKIM-Signature header names its selector in s=.

Question 3

How do I find my DKIM selector?

Accepted Answer

Open an email you sent and look at its DKIM-Signature header: s= is the selector.

The email header analyzer reads it for you.

Question 4

Why does the DKIM checker find no key?

Accepted Answer

Your service may use a selector no checker can guess, like the random ones Amazon SES uses.

Type the selector from one of your emails and check again.

Question 5

Is a 1024-bit DKIM key OK?

Accepted Answer

A 1,024-bit key still passes.

RFC 8301 says signers should use at least 2,048 bits, so rotate if your service offers it.

Question 6

Is the DKIM checker free?

Accepted Answer

Yes, the DKIM checker is free, with no sign-up.

Free DKIM Checker (+ Guide)