Try looking for an earlier version of prefs.js, e.g. prefs-3.js, and replace the current file:

https://support.mozilla.org/en-US/questions/1324156

If the mozillazine site is not responding, open the cached page from Google,

Thanks for the quick response.

With TB shut down:

I renamed prefs.js to prefs.js.bak. (prefs.js date 5/9/2021 after the problem) I renamed prefs-2.js to prefs.js. (prefs-2.js date 1/10/2021 before the problem)

I restarted TB and observed NO change. That is, I see the TB welcome screen and the Set Up Your Existing Email Address dialog.

Can you suggest another fix?

Should I return the prefs files to their original names before proceeding?

thanks...

Are there any other prefs-N.js files? Open them in a text editor to see if they contain the account information, as that is what is missing in the damaged file or even the older ones. If there isn't a 'good' js file, you might have to add your accounts again, but fortunately it shouldn't be too hard to recover the mail and other data.

Thanks.

Neither the original prefs.js nor the prefs-2.js which I renamed to prefs.js has m37787v5.Default User account information.

However, prefs-1.js (dating back to 11/2020) does. It has the following three records:

user_pref("mail.root.pop3", "C:\\Users\\David\\AppData\\Roaming\\Thunderbird\\Profiles\\m37787v5.Default User\\Mail");

user_pref("mail.server.server1.directory", "C:\\Users\\David\\AppData\\Roaming\\Thunderbird\\Profiles\\m37787v5.Default User\\Mail\\secure.fsr.com");

user_pref("mail.server.server2.directory", "C:\\Users\\David\\AppData\\Roaming\\Thunderbird\\Profiles\\m37787v5.Default User\\Mail\\Local Folders");

So, should I rename prefs-1.js to prefs.js and give TB another try? And should I delete the other two profs.js files that don't have any account records?

Thanks

Sure, go ahead and try that, but don't delete the other file backups until the system is back to normal.

Thanks.

I backed-up prefs-1.js and renamed prefs-1.js to prefs.js and relaunched TB. I'm now greeted with my account screen and Local Folders (see image below). But there is no Inbox nor Inbox folders and Local Folders is completely empty. That's some progress so I guess I'll leave the latest prefs.js as it is.

Is there something else we can try?

Thanks in advance...

If there's no working prefs file, and you don't have a working profile backup, it's probably best, and fastest, to simply add your accounts, and recover the local mail from whatever profile remnants remain but are currently unrecognized. Open the profile folder and close TB, then look in the Mail (POP accounts) or ImapMail (IMAP accounts) for mbox file in account subfolders, e.g. Mail/<popservername> or ImapMail/<imapservername>. The mbox files are large files with no extension, named after folders, e.g. Inbox. Copy them into Mail/Local Folders of the current profile, and then find them under Local Folders in the Folder Pane when TB restarts.

When I opened TB this morning I found that Inbox and all of its sub-folders had populated TB's Folders pane. This happened BEFORE I executed any of the instructions from your last post. In fact, I've done nothing except for the prefs.js work we discussed yesterday. On closer inspection I found that all the Inbox sub-folders that received some attention (e.g., storing a message) just before the crash cannot be opened but all the other folders can be opened and show the message contents I expect. The Inbox folder itself can be opened but is empty. (see Image below)

Does this change the plan of attack?

I still think the previous suggestion to create a new profile, add the accounts, and transfer mail from the old profile to the new, is the best and fastest route to a normal setup. I don't know enough about your system to offer anything better.

I realize that I do have back-ups of my profile. The newest is 5/7/2021 which is plenty recent but is likely a backup of the already damaged profile. The older backup is from 4/26/2021 and most certainly contains an undamaged profile but the last two weeks of mail are missing.

If I restore my profile from the 4/26/2021 backup to bring TB back to normal, could I then transfer the un-extensioned mbox files Drafts, Inbox, Junk, Sent, and Trash from ...Profiles\m37787v5.Default User\Mail\secure.fsr.com in the more recent backup to bring the restored profile up to date with the most recent mail?

I see this as a similar strategy to your suggestion of creating a new profile, adding an account and transferring mail from the old profile. Except I'd be using an existing, al beit old, profile and account and transferring mail from the newer damaged profile.

Worth a try?

Sure, that should work, as long as the mbox files from other profiles are copied into Mail/Local Folders, renaming them if necessary.

My plan was to restore my profile to its current folder, i.e., F:\Files\Technical\Settings\TBIRD\Profiles\m37787v5.Default User\Mail\secure.fsr.com. To me this seems most straight forward and I think I understand how to do it.

But you're suggesting that I restore the profile to F:\Files\Technical\Settings\TBIRD\Profiles\m37787v5.Default User\Mail\Local Folders and then copy the mbox files (renaming them if necessary - ???) to that location.

After 17 years of having the profile under ...\Mail\<popservername> I wonder - why is it necessary to change? I'm not resistant to changing to ...Mail\Local Folders but I think I may need some step by step instruction to do so. If you feel this change is necessary can you help me accomplish it?

I've restored my 4/26/2021 backed up TB m37787v5.Default User folder to it original location in F:\Files\Technical\Settings\TBIRD\Profiles\m37787v5.Default User. I launched TB and everything seems to be working just fine as it was on 4/26/2021. So I'm convinced that the 4/26/2021 backup is not compromised.

So how do you suggest I proceed?

Should I simply restore the un-extensioned files Drafts, Inbox, Junk, Sent, and Trash from my 5/7/2021 backup into the F:\Files\Technical\Settings\TBIRD\Profiles\m37787v5.Default User\Mail\secure.fsr.com folder?

Or as you suggested in your last post, should I copy the 5/7/2021 mbox files "...into Mail/Local Folders, renaming them if necessary." If this is what you recommend, I have some questions.

Should I restore only the Drafts, Inbox, Junk, Sent, and Trash files into Local Folders or should I restore the entire contents of ...Mail\secure.fsr.com into ...Mail\Local Folders?

What might need renaming?

How will TB know where to look for my mail?

Thanks for any guidance you might provide.

If you rename an mbox file after copying it to Mail/Local Folders, before restarting TB, e.g. Inbox to InboxFromBackup, then you'll be able to distinguish the current Inbox from the copied one. The folders will appear under Local Folders in the Folder Pane when TB restarts.