Thunderbird 78.4.1 connections & setup in meltdown mode.

I have a big kerfuffle going on, but I'll take one step at a time. T'bird 78.4.1 - an automatic update
has two main problems: profiles, and the internet connection configurations. The immediate problem is this: after the 'update,' there was suddenly no internet connection. We can get webmail from the ISP's server, so the password etc. are OK that way, but not with T'bird. The only way to get connected is to enter NONE in the SSL layer, which produces a bright red popup warning the size of a moose, saying THIS WILL LOG YOU INTO THE SERVER BUT IS UNENCRYPTED, DANGEROUS, etc. etc.. It is not the responsibility of the ISP (a cable company,) to sort out T'bird and Mozilla people are helpful when they can be.........

Can anyone here guess why the only acceptable SSL encryption status is "NONE," and yet the settings work fine fetching webmail? What can T'bird has misconfigured, if that's right terminology? Eh?
Thanks for any suggestions.

First and foremost, never let anything auto update if you can help it. Read Sig below.

Thunderbird can be a major pain in the ass with its BS. I never let it update until I want to, and even then I backup the profile folder just in case. So try this once since I'm not too sure what's going on since this more than likely worked before. Go back to that Thunderbird thread you chimed in at and in there I gave a link to portable Thunderbird. Pick version 78.4.1. Now copy and paste your current Thunderbird profile folder contents to the portable one and see if you still can't make an encrypted connection.

By chance, what is the domain for the email address that won't work? Is the TLS Cert self-signed or something? Don't post the entire email address, just the domain. Be it be gmail.com, yahoo.com, etc, etc.

F22 Simpilot said:

. Pick version 78.4.1. Now copy and paste your current Thunderbird profile folder contents to the portable one and see if you still can't make an encrypted connection.

Would it matter if I used an even newer version?

I'd use the version you got updated to to keep the constant without introducing any variables.

Again, what is the domain of the email address? If it uses a self-signed Cert. it may be an issue. Just doesn't make any sense as to why "none" has to be selected in order to work. I can look at the domain and see what it offers for TLS/SSL.

The domain is sourcecable.net

This seems to be Mozilla's explanation. Too bad for me and for a lot of other folks.

So that domain has all kinds of issues. You can see here: Domain Health Check - Online Domain Tools - Blacklist, Email, Website, DNS - MxToolBox Enter sourcecable.net

I'd go to your ISP and ask them to fix their crap. Also, their website doesn't even load as an HTTPS connection. If you load it as an HTTPS connection the whole website is messed up.

For the heck of it, in Thunderbird try mail.sourcecable.ca