[stunnel-users] tunnel for IMAP/SMTP

Good day. I need to be able to use Thunderbird to connect to a mail server (IMAP/SMTP) that has an obsolete TLS version (1.1) and I don't want to low the TLS minimum version on my computers. For this need I would like to use stunnel between Thunderbid clients and the mail server. I tried to use tutorial [1] plus "sslVersion = all" option, but I think the guide is quite incomplete. Do you have any other guide/tutoral that is more complete? Thank you

[1]: https://petermolnar.com/secure-smtp-and-imap-sessions-with-stunnel/