A belated note: TLS 1.0 and 1.1 support ended with Thunderbird 68.4

Once upon a time, we did not have to worry about connection encryption.  everyone connected in plain text and often did not even need a password.  How time have changed, over the last 20 years, connection encryption has become a defacto standard. So now there is not only the End of Life dates for Operating systems (windows 7 14 January 2020)  but these encryption protocols come out with new versions and older versions are cryptographically broken and have to be removed from active use.

The time has come in Thunderbird for the end of life of TLS version 1.0 and 1.1.  TLS 1.0 was technically "end of life" 30 June 2018 but for reasons, I do not grasp the agreement between Apple, Google, Microsoft, and Mozilla to retire support for these aging cryptographic protocols is for version 1.0 and 1.1 together. Firefox has now retired them in Version 74, and as Thunderbird is built on the Mozilla platform it is also retiring them at the same time as Firefox ESR removes it in Version 68.5.

So what does this mean to Thunderbird mail users?  For most people it means nothing.  Your mail provider will have been proactive in retiring old protocols and maintaining their PCI DSS compliance so the change will have no impact at all.

For those who use mail servers that do not have proactive administrators, you will not be able to connect to the mail server to get your mail.  If you suspect this might be the case, open the error console (Alt+Shift+J) and clear it (trash bin icon) then attempt to get your mail.

You will see errors about incompatible connection or security issues. I do not have access to a noncompliant email server to offer examples.  But as an alternative, you can go to the ssl-tools web site and put in the part of your email address after the @ and check in the report that your mail server supports TLS versions greater than 1.1