Daily notifications: Missed domain names failed to pass validation: webmail.example.com

 Symptoms

• Notification e-mails with the following content are being received on a daily basis from Plesk:

  "Could not secure domains of John Doe (login jdoe) with Let's Encrypt certificates. Please log in to Plesk and secure the domains listed below manually.
   Securing of the following domains has failed:
   'example.com'
   Missed domain names failed to pass validation: webmail.example.com
   The following domains have been secured without some of their Subject Alternative Names:
   <none>
   Could not renew Let's Encrypt certificates for Joe Doe (login joedoe). Please log in to Plesk and renew the certificates listed below manually.
   Renewal of the following Let's Encrypt certificates has failed:
   <none>
   The following Let's Encrypt certificates have been renewed without some of their Subject Alternative Names:
   <none>"

• Mail Service is enabled in Domains > example.com > Mail Settings
  
  

• Webmail is set to None in Domains > example.com > Mail Settings
  
  

• SSL it! Keep websites secured is enabled in Subscriptions > example.com > Customize > Additional Services or 
  Service Plans > Service Plan Name > Additional Services:
  
  

Cause

The “Keep secured” mechanism does not depend on options selected during SSL certificate issuing. It is just checked for installed certificates during daily maintenance task.

Resolution

To stop receiving emails about unsecured www and webmail, log in to Plesk and set the option to None::

• For subscription: Subscriptions > example.com > Customize > Additional Services and set option to None
• For service plan: Service Plans > Service Plan Name > Additional Services and set the option to None