I understand that the working direction of syncing in IMAP is from the mail client to the server.

I'd argue it's the other way round.

In a specific given situation, I would like to invert this working direction.

What are you trying to achieve in the first place?

Syncing doesn't happen in a predetermined direction. It depends on where changes happen. Syncing is accomplished by applying to one side the changes made on the other. You cannot make Thunderbird "undo" a change made on the server if that's what you mean.

Thanks both for the clarifications. Quite frankly, I wasn't 100 % certain myself, this is just what I read a number of times. Right, I could have added the original situation where the idea for this workaround originated. Let's do it now.

When I recently opened a Gmail account, I didn't realise that it is set such as to bundle pertaining messages in groups. This effect will then be replicated in the mail client, according to my impression (it could also be a misunderstanding).

After having seen how to undo this default setting in the web interface, and seemingly with success, I keep struggling with establishing the same principle in the client: The new message arrangement doesn't seem to propagate from the server.

More searching led me to https://itsfoss.com/thunderbird-threading/ and there the title Changing the default thread view

When I do what is said there, thus set mailnews.default_view_flags to 0, then click the tick button for confirmation, then for safety's sake close and reopen the client, I cannot make the thread marks go away - I have to do it manually for each and every folder.

So this is the present, modified situation. I'm set to get more practice/experience now and see what else I can do, or if I can live with it. However if you happen to have a better idea, then you are certainly very welcome to share it .)

I believe you're referring to threading, not to synchronization.

This is the official (to my knowledge) documentation. Well worth the read https://support.mozilla.org/en-US/kb/message-threading-thunderbird

Here is my own documentation on threading, duplicating the above, but it may help: You need to highlight each folder and click View>sort by>unthreaded. If this applies to just a few folders, just repeat the process as necessary. If you have many folders or plan to add many new folders, you may wish a different approach, below:

FOR NEW FOLDERS To change default for *new* folders, In config editor, you can change default that applies to NEW folders you set up: mailnews.default_view_flags 0 =unthreaded

Config editor is available at Tools>settings>general and scroll to bottom right.

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FOR EXISTING FOLDERS These steps may help: To set many *existing* folders, follow these steps: This must be done on an account by account basis.

1. select table view - the icon just to right of 'quick filter' button above message list pane
2. select a message folder and apply all desired attributes - View>sort by from menu bar (if not shown, click alt key)
3. click the icon at right side of column display in message list pane
4. select the entry near bottom 'Apply current view to...'
5. highlight 'folder and children'
6. move mouse left to see account name and move left again to display all account folders. Now CLICK. a small menu will appear to confirm setting all folders within that account.

A simpler approach is in beta, so this will get much simpler shortly.

Thanks again. Let me insert here that my interest in solving this issue is not endless. If things in this field get too intricate seen from my amateur perspective, then I tend to adapt to the makeshift, if the downsides somehow can be tolerated.

As this will require more tests and practical experience-making, this is nothing I can decide within the next hours. It also means that I cannot, at this stage, with a good conscience mark any reply as a problem solver.

I will not forget it and get back, but it may take days, or even weeks. Bear with me, if you can.

Oh, that's a surprise: I just did as you recommended below the chapter where you referenced the official TB version - ie manually set every single folder, and now there seem to be no more grouped messages.

This is what I wanted to achieve, no? Thus it doesn't look like any more practical experience were necessary.

Then let me send you my thanks, and I will gladly upvote the respective message of yours!