How to make IMAPS SSL Cert for Dovecot that works with Thunderbird

Hello all,

What are the instructions for making an SSL cert for Dovecot IMAPS?

Two methods have been tried, and work, with Evolution; however generate the following error when Thunderbird tries to connect.

Thank you,

method 1 : self signed openssl req -newkey rsa:4096 -sha512 -x509 -days 365 -nodes -keyout mykey.key -out mycert.pem

method 2 : Let's Encrypt (LE) CA Created with Certbot

ERROR TLS handshaking: SSL_accept() failed: error:14094412:SSL routines:ssl3_read_bytes:sslv3 alert bad certificate: SSL alert number 42, session=<+oooooo>