Figured it out!
When i was configuring Letsencrypt for my https connection I had commented out all of previous ssl directives… Once letsencrypt was completed and my sessions were secured I didn’t think any of the other directives were necessary… the one that Thunderbird needed was
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
once that was added it all worked great.
All the necessary ssl directives for Nginx config are
ssl on;
ssl_certificate /etc/letsencrypt/live/cloud.gregorigroup.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/cloud.gregorigroup.com/privkey.pem;
ssl_session_timeout 5m;
ssl_ciphers 'AES128+EECDH:AES128+EDH:!aNULL';
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_prefer_server_ciphers on;
Thanks
Wayne