DKIM key not visible in How to configure external DNS section

Symptoms

• Generating new signing keys and selecting them via the Active DKIM Selector in Plesk > Domains > example.com > Mail Settings is possible
• After deactivating and reactivating DKIM spam protection in Plesk > Domains > example.com > Mail Settings, a new DKIM key is not visible in Plesk > Domains > example.com > Mail Settings > How to configure external DNS
  
• The necessary keys are also not present in /etc/domainkeys/

Cause

The issue was confirmed as a bug with ID #PPPM-14160 DKIM key not visible and was resolved permanently in Plesk Obsidian version 18.0.57.

Resolution

Update Plesk Obsidian to version 18.0.57 by using the information in this article:

How to update Plesk Obsidian to the latest build?

Afterwards, go to Plesk > Domains > example.com > Mail Settings , uncheck the Use DKIM spam protection system to sign outgoing box, save the changes, check it and save the changes once again.

That should make the DKIM appear in Plesk > Domains > example.com > Mail Settings > How to configure external DNS.

# mkdir /etc/domainkeys/example.com
# cd /root
# openssl genrsa -out private.key 1024
# mv private.key /etc/domainkeys/example.com/default
# chmod 440 /etc/domainkeys/example.com/default
# chown root:pouser /etc/domainkeys/example.com/default
# cd /etc/domainkeys/example.com/
# openssl rsa -in default -pubout -out public.key
# openssl rsa -in /etc/domainkeys/example.com/default -pubout