We have a few customers that for one reason or another we don't host the website on the Plesk server, but still host DNS and email. There is no easy way to have a mail.<domain> SSL certificate generated by Let's Encrypt like it can for webmail.<domain>. I'd like to see mail.<domain> be an option for SSL generation so that mail clients can connect securely to the mail server and not have to explain to them about using 'webmail.<domain>'.