Suddenly today (Linux, PopOS 20.10, TB 78.7.1(64-bit)), I can't send mail via my ISP using Thunderbird. At first an email was rejected, saying the certificate was invalid. Viewing the certificate details, I saw the certificate had dates in the future (start on 5th Oct, end on 6th November), and as well it referred to my ISP's updated domain name: optusnet had replaced optushome quite a few years ago. Guessing that perhaps I needed to change the mail server name from optushome to optusnet, the situation became far worse for me after I tried to do so, which failed dismally, and I then changed it back to optushome. Now I get:
"Sending of the message failed. Unable to communicate securely with peer: requested domain name does not match the server’s certificate. The configuration related to mail.optushome.com.au must be corrected."
Since I can't find the server's certificate, TB has tied my hands nicely. I also belatedly guessed that the dates on the certificates might be presented in US style (M/D/YYYY) rather than Australian style (DD/MM/YYYY or YYYY/MM/DD), since today is 13th May 2021. But now I can't even get TB to check for a certificate.
If I get to the Add Security Exception popup, Get Certificate fails for mail.optushome.com.au:25 and for mail.optusnet.com.au:25 . In either case, TB says just:
"No Information Available Unable to obtain identification status for this site."
If I try "optushome.com.au" the Get Certificate says "Checking Information / Attempting to identify this site..." and several minutes pass before failing with the "No Information Available" result.
I think the key parts of the problem are that 1) TB offers no way to find the certificate(s), and 2) offers no hints about HOW to correct the configuration.
In desperation I tried "Confirming Security Exception", and now if I click Send the mail appears to be sent, then it warns me it has failed to save a local copy in my sent folder, and then shortly after I see a notification of failure to connect to mail.optushome.com.au (and the mail doesn't appear to be sent).
However, now I can't get to the Add Security Exception popup, because TB thinks it has sent the email, I suppose.
I also tried https://support.mozilla.org/en-US/questions/1083282, but that made zero difference, and I have now unset the new string. (There seems to be no way to delete it.)
openssl
, I can confirm that it is valid (“Not Before: May 10 00:00:00 2021 GMT”). // Are you perhaps still using the old host names in your Thunderbird configuration? You have to use the new host names.