Unable to send emails using Thunderbird

In some cases, after upgrading Thunderbird, it becomes unable to send emails. In that case, try a workaround by toggling the value of the option security.tls.version.min from 3 to 1. Google to find how to set that value in Thunderbird.

See also this URL: https://support.mozilla.org/en-US/questions/1295861

and also this one: https://support.mozilla.org/en-US/kb/thunderbird-78-faq#w_how-to-enable-outdated-security-protocols-tls-1-0-and-1-1