Mail is received: No valid IP addresses found for sub.example.com

Symptoms

• Email with following content is received:

  Could not secure domains of johndoe (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' 
   Invalid response from https://acme-v02.api.letsencrypt.org/acme/authz-v3/1234567.
   Details: 
   Type: urn:ietf:params:acme:error:dns 
   Status: 400 
   Detail: No valid IP addresses found for sub.example.com 
   'sub2.example.com' 
   No domains have passed validation

• Domain sub.example.com is not accessible with webbrowser

• External DNS Server is used

Cause

Domain sub.example.com has no A type DNS record.

Resolution

If the domain is not hosted on the Plesk server, delete the subdomain in Plesk.

Alternatively, set up A record for it in external DNS server.