I have edited your post so I can read it. Please no leading spaces, it places the entire paragraph on a single huge long line.

The term "threaded" has two meanings or definitions or uses or whatever, which makes asking for help all the more difficult

Threading is a very specific way of sorting email in a single folder in Thunderbird's implementation and this is expanded further with a dedicated conversation view for individual emails. The following images illustrate threading in Thunderbird.

Threading in the list view.

Threading in the cards view

There is also a sort menu for the folder on the same bar as the quick filter which enabled and disabled the sorting of messages by thread for the folder which can also be accessed from the main menu bar.

That is threading in a nutshell. It can be accessed from a number of locations in the user interface, including the main menu bar. But the concepts are the same, regardless of the method of access. The choices you make affect the currently selected folder. In the support topic which has been repeatedly linked, are further steps you can take to eliminate threading as a default, something that was introduced as a new default about 18 months ago with version 102

All this does is hide e-mails that are even threaded or unthreaded

I think you are perhaps the only one of millions of users with that experience. However I think the experience is more perception rather than fact. Once a folder is no longer threaded, individual emails are sorted in the list in the sort order specified , rather than having them appear in the thread group. SO while whatever email you have selected will be retained when the threading is turned off, other emails will be sorted into the list in their own position and may simply disappear from view based on their new list location. But nothing is supposed to be hidden at all.

If you want to see the conversation the email belongs in, which from what I am putting together is more what your expectation of a thread is, right click the message and choose to open the email in conversation. This is basically the same as Threaded view, but an on the fly search is undertaken for any messages stored anywhere in your profile that belong in the more holistic view of the topic as a conversation. The following is a extract from a conversation tab.

Note the addition of a location column on the right which shows the folder the message was located in.

There is another loose and incorrect interpretation of a thread in relatively common usage, as the quoted replies within a single email. This is not a thread and never has been. But like many old wives tales it refuses to go away. Unfortunately education is no way to eradicate these incorrect terms as those who use them cling to them like they are alternative facts and those correcting them are the ones in the wrong.

There is an addon that emulated the Gmail approach to conversations, called conversations, you might want to have a look at it as your expectation of a thread appears to be more in line with the google way of looking at things as a conversation rather than as a thread. https://addons.thunderbird.net/en-US/thunderbird/addon/gmail-conversation-view/?src=ss

Personally I have modified my settings to place copies of replies in the same folder as the message which they are replying to as that includes my reply in the basic threaded view. (Account settings > copies and folders) But that is me making allowances for the way the software works. It does have a limitation that original messages are not threaded when I get a reply to them, but the conversion view takes care of those few where the entry in my inbox is obviously a reply to something I sent.

I quoted David because he was the most helpful up to that point. I'm more tempted to quote Nick At Night, but I don't see what good that would do.

There's a lot here and I'll go through it one at a time. I'm sorry you felt a need to insult me, but you also gave a lot of information.

I didn't know about the leading spaces. Where could I have found that out?

I'm not looking for ways to see threaded messages. I don't want or need threaded messages at all. What I want and need is the way things worked before: all e-mails sorted by date if I chose them to sort by date or all messages sorted by the person or people I sent them to if that's what I need. Now, when I sort by date, many messages are missing because thunderbird threaded them without my knowledge or consent. Nothing whatsoever to do with the menu bar that also includes date, size, etc.

Is there a way to take the automatic threading away? Not merely taking away the default to future files, but current files. The default changed itself back, btw, as Nick At Night mentioned.

That sort bar where I can check either threaded or unthreaded. Why am I not allowed to see both? In date order or alphabetical order or whatever I sort by. That's what I mean by it hides the other. If I click threaded, one bunch of e-mails shows up. When I click unthreaded, a different bunch of e-mails shows up. I no longer get to see everything. Also, when I see the threaded files, they are not expanded unless I click on them one by one. Then they all open and I have to close them all one by one. The computer software is adding work and taking away time. Shouldn't it be doing the opposite?

I doubt if I'm the only one with this problem. I saw many other complaints.

I kept seeing how to change the default for future files and folders, not how to get rid of the default on the files I already got.

Then there is how the software decides what a thread is. If I reply-all to a sent e-mail to send a new e-mail to the same people, with a new subject, the computer puts them together. My reply-all option for e-mail I have sent in the past is now taken away from me because thunderbird will thread them. I don't want or need them threaded, but want and/or need them as individual e-mails.

There is an e-mail I sent to a group on April 2, for example, that I want to do a reply-all on, but I have not seen that particular e-mail because I don't know what thread it is in, assuming the thread is visible. When I do a search for that e-mail using "search messages," it shows up, but looking under date, when I sort by date, doesn't show it to me. Looking under the names of the people it was sent to, when I alphabetize the list, does not show it to me. Do you know how I could find it? I can't right-click the message

"Once a folder is no longer threaded" is a phrase you wrote which gives me hope. How do I no longer thread it - thread is not selected on the menu bar so I hope what you wrote means there is another way to unthread? I can't "right click the message and choose to open the email in conversation" if I can't find the message. That's also what I mean by invisible.

I'm not looking to see a conversation. I'm looking to see an individual e-mail. If I want to see an entire conversation, I can always alphabetize by subject or recipients. If I can't see all the e-mails, I can't even do that. That is why I feel the same as Nick At Night about automatic threading. I am refraining from using capital letters.

Seeing the multiple locations in your conversation tab scares me into wondering if the threading is more pervasive than I've found so far. I can't even reverse threading on one location, sent mail, never mind multiple.

I have not defined threading as "quoted replies within a single email." I'm defining it as multiple e-mails that the computer has linked and put together.

I do not use google. I do not have expectations of threads or conversations because I want and need all e-mails to stay separated from one another, not threaded. That the definition of how individual e-mails are linked is decided by someone other than the user is all the more frustrating.

You seem to want to link e-mails. I do not. It hinders my work and even my fun. I really do appreciate the time you took to write that message above. I hope putting replies in paragraphs helps you read my responses. Thank you - Ken

I moved all my sent mail to a new directory, thousands of messages, for I have been using thunderbird for a long time, and there are 82 messages that are not showing up. How do I get them back? Could this be related to the "mandatory threading" I have suffered with?

I further edited the original post for readability.

If there are messages not showing, either in threaded or not threaded (doesn't matter) then as a first step right+click on the folder and do properties > repair folder

You had a new solution and I got my hopes up. But it didn't work. The messages still don't show, but the number of messages it says there are in sent mail shows that they are not deleted. Just invisible.

What would the second step be?

> What would the second step be?

Help > Troubleshoot Mode.

Also, check ALL the combinations of choices under View, especially View > Messages and View > Theads. (Although perhaps you already did that?)

The View stuff I tried. The troubleshot mode scares me because it disables addons, which I assume would include calendar/lightning and goes to default mode, and what would that do? I fear this might be beyond my capability to restore.

You can ease your concerns by reviewing https://support.mozilla.org/en-US/kb/troubleshoot-mode-thunderbird

Dear Ken,

I have had this problem too. My Sent file of 31,000 messages was reduced to a list of about twenty. All the View options were irrelevant. Threading or Unthreading seemed to make no difference.

After reading this thread, I selected the problem folder in the sidebar and right-clicked. I didn't make any selections from the resulting menu because they didn't seem relevant. When I looked at the list of files again—they were all back there!

I have no idea why this should be, but I offer it as a possible fix.

Best regards, and utmost sympathy for your frustration,

7713b24