There is no supported downgrade path. None!

I found that out when I tried to reuse a previous profile and it got crushed by the new TBird, too.

So, as a moderator, your telling us Mozilla is saying accept it or jump ship. Why? Is the new version so incompatible with the older versions they don't work together? What has become of long term users opinions? Tossed out with the resat of the rubbish, I guess.

As a Thunderbird user I think you as a fellow user need to get an understanding of a lot of things.

1. Thunderbird is not produced by Mozilla. They withdrew their development support more than 10 years ago. Thunderbird is not listed as one of their products because they do not make development decisions for it per se. https://www.mozilla.org/en-US/products/

2. Thunderbird is developed by the Thunderbird community project and another Mozilla owned subsidiary, Mzla corporation funded by user contributions. https://www.thunderbird.net/en-US/about/

3. Thunderbird is an application built on what used to be called Geko and now as "the Mozilla platform" this is shared low level code built for Firefox and shared by Thunderbird. This means that the Thunderbird development team function independently, but in some things only get what the Mozilla platform delivers. Much of the profile backward incompatibility/compatibility comes from this level (the profile managers are about identical for instance)

Thunderbird is now in a period of relatively rapid change following almost a decade of stagnation, where code was cobbled together so Thunderbird could continue, but it was certainly not an optimal situation and maintenance that should have happened did not. Largely in that period Thunderbird developers found out the platform had changed when Thunderbird stopped building. This resulted in something that worked, but the band aids were almost replacing the base code in some parts.

Because of the urgency to update some parts of the program, before there was no program, a decision was made to not add to the complexity of the changes required by building in backward compatibility. So now if a file format has to be changed, the code is written to migrate the file, and maintain it going forward. No one writes the code to convert the new formatted file to the old format.

In the past couple of years many things have changed, including the format used in the file system to store contacts, calendar and recent actions. Additional to this the platform code has changed with regard to management and storage of encryption certificates (used by the TLS/SSL connections most providers require and other bit and bobs.) These changes are not really documented beyond the bug in which they are implemented. SO there is no list that says there was a new file format for whatever from version 68 for instance.

Hence to the forced updates. This low level code is indeed mostly Mozilla code, but the Thunderbird developers saw no real reason to fight the Mozilla approach as the use of old versions of software is a little like inviting typhoid Mary to tea. Unpatched software was considered to be a worse risk than loosing some users that objected not being able to simply opt out of upgrades, and because of the way it is structured it does not affect the vociferous Linux community. So even if you change the settings to ask before upgrade, you will be prompted on every restart.

There is a command line method to force the use of an old profile. I do not recommend it as it will force the profile to be used and is really meant for the developers and those testing software, but there is no guarantee as to what will be lost in the reversion. (all contacts with one version as the MORK data format the files were written in was retired and SQLITE files was implemented as a replacement). I discussed it's use in a blog post back in 2019 and Thunderbird version 68. The repercussions have got worse since then for going back, and I will not help you if it blows up in your face as downgrading is not supported and I honestly have been things to do that help those that shot themselves in the foot.

One thing that has been and is being pushed is forcing folk off old versions of software. While like an old shoe it is comfortable, also like an old shoe it may also have a hole to get the water in. You only have to look at the number of security vulnerabilities that are fixed in each point release to understand that the older the software gets, the more likely it is someone will exploit the holes. This link is in every set of release notes, under the heading security fixes. Few even look there. https://www.mozilla.org/en-US/security/known-vulnerabilities/thunderbird/#thunderbird115.9

Personally I have huge issues with a lot of the Thunderbird 115 supernova changes. I actively dislike a lot of it's user interface and think some poor choices were made with regard to user interface design. I am however using it (modified with customized toolbars and the like) as it is a safer place to be that in the past.

I understand that occasionally the release cycle gets ahead of the add-on author that maintains your favorite add-on. I even understand when they (the add-on authors) get frustrated by developers that pull the functionality they need to actually release an upgrade. There are many issues, and many competing points of view.

Matt,

I honor and appreciate you. You have done here the one thing I was most complaining about. I wish someone had simply pushed your (or a similar) detailed explanation of what and why this was happening instead of just knocking everyone over the head with it. I scanned through the forums and there are LOTS of similar angry posts.

I for one, first tried to use the upgrade, but found three terrible problems. First, half my email and most of the last 6 months were lost and not downloadable from my normal online accounts. Second, my calendars disappeared. Third, my filters were gone.

I went in search of any alternate. The most compatible I found was SeaMonkey, but it's kind of flakey to use. It wants to be a browser first and an email client second. Finally I decided, without the calendar working, I might as well opt for ALL Google - Chrome, Calendar, and Gmail integrated in development. However, it has it's problems like no alpha sorting in emails, offline work is not as efficient, and calendar lacks all except the rudiments of style formatting.

Today, I had to come back to TBird to find an email and found all my calendars working just fine. My filters were in place and it looks like I may be able to live with this upgrade. I hope so. I've always lauded the independent thinking.

I'm still pissed over the high handedness of the process, but I really do appreciate you willingness to write so I and others can finally understand.

Thank you, Dr. Ken Rich

I do have to wonder if your experience was exacerbated by your choice of antivirus product. Windows defender causes few problems, almost all of the paid products get over protective at limes, or all the time, and kill attempts to synchronise data with the cloud. The result is things are mysteriously just not there. This applies to any cloud linked data like calendars, contacts and imap mail accounts.

I did have a feeling Thunderbird had led you down the garden path of a new profile, asking for accounts etc again on upgrade. A rather nasty bug in my opinion. But having things automatically reappear sort of puts paid to that idea.

That's a good thought. However, I've found that most commercial antivirus programs don't help me any better than Windows Defender, so that's all I use.

I appreciate this dialogue. It will help others who come searching for similar answers.

At this point, I've taken you suggestions and reverted back to TB. Now, if I can figure out a few small tweaks, I'll be happy.

Thanks.