In your Thunderbird go to menu Help > Troubleshooting Information > Profile Folder > Show in Finder, then quit TB. In the TB profile folder (probably named somewhat like abcd1234.default-release) go to folder "Mail" and open it. You should see a sub-folder "Local Folders". Make a screen shot of the contents of Local Folders.

Thank you Mapenzi for this guidance. I am so grateful.

First I should explain: As of the update, I now have two accounts appearing in my Thunderbird sidebar. One is my email address with Inbox in the dropdown, nothing else. The second is my email address + (IMAP) with all my usual non-local folders. Then below is Local Folders, and it has only Trash and Outbox in it. This is where my many local folders used to be, obviously.

So: I did as you directed. In Profiles, I have a folder called ImapMail. There is no Local Folders folder in it. The other folder, called just Mail, has a folder called Local Folders. My missing folders are not there. Only: msgFilterRules.dat, Trash, Trash.msf, Trash.sbd, and Unsent Messages. Then another folder for Smart Mailboxes.

Does this tell you anything? I can’t imagine why the local folders would just disappear completely. There are hundreds of important emails in them…

Thank you for whatever help you can give.

So: I did as you directed. In Profiles, I have a folder called ImapMail. There is no Local Folders folder in it. The other folder, called just Mail, has a folder called Local Folders. My missing folders are not there. Does this tell you anything?

You searched in your actual profile folder and Local Folders probably don't contain your lost messages, but you should still verify the contents of Trash.sbd .... I have a suspicion that you created an new profile during or after the update. Does the folder "Profiles" in Thunderbird contain more than one or two folders, and if so which are there contents. Specially verify if they contain "Local folders" ! Another possibility could be that you had delocalised your Local Folders in another directory than the profile folder.

Trash.sbd only contains a doc called Unsent Messages. Were you able to access the 2 screenshots? Those show the contents of Mail and ImapMail.

I don’t know how I would have created a 2nd profile, or how I would have delocalised my Local Folders. Are there ways to fix though?

THANK YOU

Trash.sbd only contains a doc called Unsent Messages. Were you able to access the 2 screenshots? Those show the contents of Mail and ImapMail.

Yes, I have seen your screen shots but I couldn't find your missing folders and messages in ..../Mail/Local Folders/....

I don’t know how I would have created a 2nd profile, or how I would have delocalised my Local Folders. Are there ways to fix though?

And since I cannot look over your shoulder on your Mac screen I have to ask for screen shots. Your missing data are not visible in Local Folders, so I continue to search somewhere else and ask questions which you might consider as superfluous or even stupid.

I don't know what happened during your TB update. You describe that "I now have two accounts appearing in my Thunderbird sidebar. One is my email address with Inbox in the dropdown, nothing else." This is not normal! If you only had an IMAP account before the update, where does the second account come from? Did TB after the update start with a request to set up "your existing email address"? But you are very certain that in folder "Profiles" there is no second profile folder that you won't verify?

The contents of the "smart mailboxes" in your "Mail" folder tells me that you are using (or have been using) a so-called "saved search" or other virtual folder with the name "tags". Maybe in your Local Folders you created such a virtual folder containing sub-folders ?

Your questions are great! I appreciate your help and how thoughtful you are about trying to figure it out. I hope nothing I said indicated otherwise.

To answer your questions: 1. If you only had an IMAP account before the update, where does the second account come from? GOOD QUESTION! I have no idea 2. Did TB after the update start with a request to set up "your existing email address"? No. 3. But you are very certain that in folder "Profiles" there is no second profile folder that you won't verify? Yes. 4. The contents of the "smart mailboxes" in your "Mail" folder tells me that you are using (or have been using) a so-called "saved search" or other virtual folder with the name "tags". Maybe in your Local Folders you created such a virtual folder containing sub-folders ? I did not knowingly do so.

I do have Time Machine but not sure where to look. I think this is all beyond me. Perhaps I can find someone to look over my shoulder and help, as you say. So frustrating! But again I thank you for trying to help.

I am grateful to you because since the beginning of this year you are the first person to respond to any of my messages describing solutions and/or asking for more infos... unlike at least 150 other people which didn't bother to comment my messages!

If you have an external hard disk for your "Library" backups please plug it to your Mac and in a Finder window verify if you have made a backup some days before your TB update. I join a screen shot of my TimeMachine backup disk with more or less regular backups of my data, so you know what and where to look for.

Well I think I am really lucky to have found you! Yes I have an external disk, and thank you for telling me to go to the Library folder. What’s next? I looked there for Local Folders, Mail, Thunderbird… Didn’t find these.

What’s next? I looked there for Local Folders, Mail, Thunderbird… Didn’t find these.

It's a long way to go!! Look at my screen shot from March 5th: select a Time Machine backup (a date) made shortly before the loss of your Local Folders. Then go to Macintosh Data > Users > username > Library > Thunderbird > Profiles > profile name >Mail > Local Folders (see image with path to Local Folders in Time Machine) Copy the folder "Local Folders" to your Desktop.

In Thunderbird via Help go to Troubleshooting Info > Profile Folder > Show in Finder as described in my first reply, then quit TB. Go to the "Mail" folder and delete Local Folders. Then drag the "Local Folders" backup which you just copied from Time Machine to your Desktop and drag it in the folder "Mail" in your actual profile folder. Restart TB and report good news (i hope so!)

I actually already tried that and could not find Thunderbird anywhere, strangely enough. I discovered that I have 2 different folders under Users (with 2 variations of my name), one dated Sept 2024 and the other July 2023. (I don’t know why there are 2, but…) Neither of these folders contains a subfolder called Library. HOWEVER in Macintosh Data there is another folder called Library. Unfortunately, that does not have Thunderbird in it. I also did a global search for Thunderbird and the only thing that come up was the application. I’m sorry this is so complicated!

Neither of these folders contains a subfolder called Library.

When you navigate in the Time Machine Finder window up to Users, then select your "user" (Home) folder, click on the "Go" menu, hold the Alt (Option) button you will see "Library" in the drop down menu. When you select "Library" does it appear in your Home folder in Time Machine?(see image)

HOWEVER in Macintosh Data there is another folder called Library. Unfortunately, that does not have Thunderbird in it.

This is the Macintosh HD Library and the wrong directory to look for the "User Library"! Did you read my private message?

Those were good instructions on how to find hte library - thank you. Here are screenshots of what they contained. Again could not find Local Folders. Such a mystery and frustrating! Thank you again for the help, truly.

Here are screenshots of what they contained. Again could not find Local Folders.

I do see a "Local Folders" folder in the "Mail" folder at the bottom of your second screen shot!! (see image). What do they contain?

I'm sorry, I wasn't clear. Yes, there is Local Folders, but I meant MY local folders were not there. See screenshot - just Trash and Unsent Messages.

I wonder whether you have really searched the Local Folders in your Time Machine backups. I cannot verify since your screenshots never display the path to the files and folders. Look at my screen shot from 3/6/25 and you will notice the path to Local Folders in my backup in Time Machine. Maybe there still is a chance by going further back in Time Machine by searching a profile backups from January or February

Searching for your missing folders is like looking for a needle in a haystack. When I'm doing that I would sweep up and disperse the hay in all directions. On a PC screen this means have the possibility to look here and there, open many folders and look what is in them instead of depending on screen shots from which I don't know exactly where they have been made. I am sorry but I cannot continue like that. Try to find some friend you trust enough to show him your PC screen or ask a professional IT specialist whom you would pay.

Bonne chance ...

Thank you again for your help!