Removing Lets Encrypt Certificate from Plesk hosting and webmail.

Once you move a domain web hosting out to an external provider the Lets Encrypt Certificate can not be renewed

Removing the Lets Encrypt Certificate from the HIS Plesk Hosted account

Removing the cert from the domain is done by Domain Tools "Hosting Settings" and selecting
Certificate: None
Click OK to save.

Removing the Lets Encrypt Certificate from webmail

1- Select "domains," then select your domain and then select Domain Tools "Mail Settings."
For "SSL/TLS certificate for webmail."set the drop down to "Not Selected".
Click OK to save.

2- Open the Domain Tools "SSL/TLS" icon and remove the webmail subdomain certificate from there, too.
Click OK to save.