Dang it! Thunderbird Quit Working!

Re: Windows 11 and Thunderbird 140.0.0 (64-bit)
(July 22, 2025)

After having been recently installed as a replacement for Windows Live Mail, Mozilla Thunderbird worked fine for a couple of days, then stopped receiving mail from four of my five email services, with Thunderbird initially coming up with complaints about their SSL/TLS certificates not matching the domain name.

That seemed strange, since as far as I knew, none of them actually have a CA certificate. What the four affected services have in common is that they are all associated with non-commercial non-encrypted domains (HTTP rather than HTTPS). So, not being skilled in IT, I just shrugged, and assumed that an automatic update must have changed something having to do with SSL/TLS handshakes, and Thunderbird wasn't going to like non-secure servers anymore.

I spent a whole day reading about ways to fix this, all to no avail. I even tried a couple of different email programs (Mailbird and Postbox); they worked, but one is sold on a subscription basis, and the other one has been abandoned by its developers. I'd had just about decided to abandon Thunderbird and try the new Outlook once again, but decided to give Thunderbird one last go … the "nuclear option".

But rather than uninstalling the whole program, I decided to first try just deleting and reinstalling the four troublesome email accounts. This is easily done by …

1. … right-clicking the account name in the "Mail" pane, then selecting "Settings", and then clicking the Delete button.
2. Don't tic the "Remove message data" box. Your folders and mail for that account will be preserved. Then click Remove.
3. Then return to the "Mail" pane and re-install the account using the automatic account setup wizard as you did before. If or when asked whether you really want to have Thunderbird skip the security-checking protocols, answer "Yes".

Providentially, this solution worked for me, and all four of these accounts are now happily up and running once again. I don't know why. Will they keep working … who knows. I tried Thunderbird once before when I got mad at Microsoft for dumping Outlook Express, and as I remember, it proved to be annoyingly cantankerous, so I gave up on it. If it causes any more headaches, I guess I'll just have to bite the bullet and go with Outlook (New).

Altertatively, all this spotlighted the non-secure mode of these four websites (all mine), and the reality that it's time to bring them up to date. That'll be a great way to occupy my time over the next couple of weeks.