Thunderbird also re-selects Sent and All Mail for syncing even when I don't want it
I go into Account->Settings->Synchronization and Storage->Advanced to select the folders for synchronization, and the "Sent" and "All Mail" folders are specifically *not* selected (see first screenshot).
However, if I now send a message, and then re-open the dialog box, it has silently added a checkbox next to "Sent" for synchronizing (see second screen shot).
Similarly, if I archive any message in my inbox, Thunderbird silently adds the "All Mail" folder for synchronizing (see third screen shot).
This is similar to the bug where Thunderbird automatically selects these folders to "subscribe" to, when I sent or archive a message: https://support.mozilla.org/en-US/questions/1226188
These are catastrophic bugs for me because my Sent and All Mail folders are huge (as I imagine they would be for a lot of people) and I don't want them synced. Once Thunderbird starts trying to sync one of them, there's nothing I can do to cancel it without restarting Thunderbird, which means I now have to do that every time I send or archive a message.
I can't think of any reason why these bugs would be affecting just me; but I assume anyone who is affected by these bugs on Thunderbird will have to migrate to a different email program if they're not fixed.
Alle svar (3)
This is a duplicate of https://support.mozilla.org/en-US/questions/1226188 as far as I see, so I am closing that as a duplicate.
If you think it is a bug you might want to file a bug report. in Bugzilla. https://bugzilla.mozilla.org/ Personally I think automatically subscribing a folder that is referenced by putting mail in it is exceedingly user friendly.
There is a difference between subscribing to a folder and selecting it for offline use. You can subscribe a folder, see the messages it contains and have no local copies of the message itself. That is the process you describe in Message Synchronisation and under the advanced button. If you are worried about space, why keep messages for any folder on the local device? The only real benefit is to have a locally cached copy to speed up display.
I would suggest you use the advanced button in Synchronization and storage to select which folders you want stored locally for offline use. That way only sufficient information is stored locally to populate the lists in the user interface. Search of message bodies will be either very slow or useless, but configuration of the software to your liking is why these settings exist.
You might also want to right click the account in the folder pane and select subscribe to subscribe to the folders you want to see. That is if you have turned off the option in Server settings > advanced to show only subscribed folders.
Note that right clicking any folder in the folder pane and selecting properties will also allow access to that folders "offline" status under the synchronization tab.
That's why I posted these as two separate bugs, these are two separate issues.
https://support.mozilla.org/en-US/questions/1226188 is about the fact that Thunderbird 'subscribes 'to these folders even when I don't want to subscribe to them.
https://support.mozilla.org/en-US/questions/1226546 (this post) is about the fact that Thunderbird re-selects these folders for *synchronization*, even when I have specifically chosen not to sync them.
Even you think re-selecting a folder to "subscribe" to is acceptable behavior, re-selecting the folder for *syncing* is worse.
Based on your reply, are you sure you read my description of the problem? I know how to select and de-select folders for synchronization; my post is about the fact that Thunderbird ignores what I've chosen, and goes back and silently re-checks the boxes for "Sent" and "All Mail" when I move messages into those folders.
As you have filed bugs, there is nothing further to do here. It is now in the hands of the developers.