Cannot find domain in the certificate - Let's Encrypt

I am trying to setup an SSL Certificate for, but everytime I try to generate the certificate I get Cannot find domain in the certificate. Furthermore, when I try to access the webmail via I get the Apache is functioning normally message.

What am I missing in my configuration?


You are reading too much into the output … if you look, the certificate is issued and valid.

Webmail is accessed via, not The mail subdomain is used for postfix/dovecot - not for https.