Check DKIM using nslookup, MX Toolbox and email message headers

How to check DKIM selector DNS records using nslookup and MX Toolbox. And verify DKIM signing in email message headers.

Verify DKIM DNS records using nslookup

You can use nslookup to check the DKIM selector public key DNS TXT record

The DKIM selector uses a sub domain so the lookup format will be
selector._domainkey.yourdomain.com

Open Command Prompt

nslookup
set type=txt
selector._domainkey.yourdomain.com

exit 

Check DKIM selector using MX Toolbox

You can also use MX Toolbox DKIM Lookup tool to check your DKIM selector DNS record

https://mxtoolbox.com

Enter yourdomain.com:selector 

Check DKIM using Google message header analyzer

Last, you can verify messages are being DKIM signed using Google message header analyzer and by manually checking the message headers.

Google message header analyzer
https://toolbox.googleapps.com/apps/messageheader

Paste the email header and click Analyze.

If DKIM has been setup correctly, you should see DKIM pass in the results.

Verifying DKIM signing in email message header

You can check DKIM signing by looking for the DKIM signature in the email message header