View menu > sort by and change to unthreaded.

If I could remove this threading stuff, I could sort all the messages in my subfolder in date order. I have not had this problem before!

If I could remove this threading stuff, I could sort all the messages in my subfolder in date order. I have not had this problem before!

Did you do as Matt advised ? Select folder then set 'View' > 'Sort by' and select 'Unthreaded'

OR click on the 'Thread' column header to switch on or off as approrpriate. then click on 'Date' column header to sort by Date, click on Date again to reverse the sort if required.

Maybe you have accidentally clicked on the 'thread' column header icon which switched it on. You could remove that column - on far right of the columns is an icon. Hover over it and it will say 'Select columns to display' Click on that icon to see drop down and select the 'threads' option to uncheck it, then it will not display the column so you cannot accidentally select it. But you do need to have switched it off first.

I have noticed in recent versions (I'm on 102) that even if I turn off threaded view, it is re-enabled when I restart the program. When the question owner indicated "I have not had this problem before", I'm wondering if "View -> Sort By -> Threaded" was also automatically enabled for him recently as well?

I do believe the "View -> Sort By -> Threaded" was auto enabled and this was deliberate; decided by the developers. So, if you got an update and suddenly saw threaded enabled then it's not a bug etc.

You should be able to do this to switch it all off in one folder and then apply everything in that folder to all other folders. A recent update -Thunderbird 102.2.1 - apparently fixed the issue of inabiity to apply 'sorting by threaded/unthreaded via "Apply current view to..."

To remove the default 'thread' option from all folders in a particular account the following should work:

1. Select 'Inbox'
2. Set : "View -> Sort By -> Unthreaded"
3. Right click on the column headers to see drop down
4. Select "Apply current view to..." - select 'folders and it's children' > select 'mail account name' and then 'mail account name' again.

You would need to repeat the above last 2 actions in order to select to set on other mail accounts.

If a restart of Thunderbird is losing your settings then check to see if the following applies: Ensure you exit Thunderbird before exiting computer so that files are closed. Allow a short period before shutting down a computer, so all background processing of files can be completed. Do you have any product installed which 'cleans up' files because it is possible they are deleting the session files? Products like CCleaner , WiseCleaner or even some Anti-Virus products can provide this facility. If you use any of those products then please make your Thunderbird profile folder exempt from scanning.