I am using Lets Encrypt to issue SSL certificates on my Ubuntu 16.04 server that uses ispconfig.
When I add an email account to Thunderbird email client I get the following message:
This site attempts to identify itself with incorrect information
Wrong Site
If I view the certificate Thunderbird reports that the certificate is issued to and issued by is
Common Name is ubuntu-1.mediamix-nj.com
Organization is Servisys di Temporini Matteo
Lookup how to add a certificate into the email server software you are using.
The ceritificate files can be found at: /etc/letsencrypt/live/<cert name>/