Version 128.7.0esr (32-bit), Windows 11.

Ugh… Another guy reported something similar a few days ago and he ended up creating a new profile. He had briefly installed a beta version of Thunderbird before this happened. Is that your case as well? Did you recently install a beta version of Thunderbird?

Account settings are stored in a prefs.js file within the profile folder. If there is a problem with that file, you may be able to fix the problem by re-creating only that file rather than the whole profile, but that will still require setting up your mail accounts again, then point Thunderbird to the folder it was using to store mail for each account before.

Go to the account Server Settings. Does the Local Directory field at the bottom of that pane appear blank as well? If it's blank, does the Browse button to the right of it let you figure what is that directory, i.e. which is the folder in the filesystem where Thunderbird stores your mail for this account? Knowing this will make setting up your accounts again easier, so take note of that for each of your accounts while you're checking that if you may figure that info there.

The following article explains what's a profile and how to locate your profile folder: https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data

Go to that folder in the filesystem, quit Thunderbird if it's running, and look for a prefs.js file there. Make sure you have read&write permissions for that file and check whether there are additional prefs-N.js versions of it, where N is a number.

Post back with the results.

Thanks DavidGG. I am on automatic updates and have not installed any beta version. Help - About Thunderbird reports that "128.70esr (32-bit).Thunderbird is up to date. You are currently on the esr update channel".

I have 3 email accounts in my profile. The identity information is blank in all of them but the server settings are populated correctly. The Local Directory field in each account is not blank, it shows the correct path to my profile in \AppData\Roaming\Thunderbird\Profiles.

In my profile folder I have a prefs.js file dated 2025-02-16 and also prefs-1.js dated 2020-02-11. I have read-write access to both.

Couple of other things that might be relevant: When I am on the Account Settings tab (the one with Account Name, Your Name, etc.) there is no button to confirm/save changes - is there supposed to be? When I start to compose a new message the From field shows [nsIMsgIdentity:id1] followed by my real name in italics. If I try to send this message I get an error "Sending of the message failed". When I click OK to that I get a status message "Creating mail message" with a progress bar that does not progress. When I click Cancel on that and try to close the draft message I get "Save draft error. Unable to save your message as a draft. Sending of the message failed." There is no problem receiving incoming mail on any of the 3 accounts.

Appreciate your help.

OK. The presence of the prefs-1.js file is and indication that there may indeed be a problem with prefs.js, but you may be able to fix it as follows:

1. Quit Thunderbird if it's running.
2. Make a backup copy of the profile folder, just in case.
3. Rename prefs.js to something else, e.g. prefs.bak.
4. Rename prefs-1.js to prefs.js.
5. Launch Thunderbird.

Post back with the results. We'll look at the other things later if the problems persist.

This is what you'll have to do next if renaming prefs-1.js to prefs.js didn't solve the problem:

1. Take note of the account settings, and in particular of the Server Settings > Local Directory being used by each of your accounts if you didn't do that before. You'll need that info now.
2. Quit Thunderbird if it's running.
3. Make a backup copy of your profile folder, just in case.
4. Rename prefs.js to something else, e.g. prefs-1.bak.
5. Launch Thunderbird. A new prefs.js should be automatically created and you'll have to set up your mail accounts again.
6. After setting up each of the accounts, go to Server Settings and use the Browse button to tell Thunderbird to use the same account folder that it was using before.

When I am on the Account Settings tab (the one with Account Name, Your Name, etc.) there is no button to confirm/save changes - is there supposed to be?

Not only there is no button to save changes, but changing any setting seems to have an immediate effect, you don't have to close the Account Settings tab nor anything.

When I start to compose a new message the From field shows [nsIMsgIdentity:id1] followed by my real name in italics.

Interesting observation. This and the fact that the other account settings panes appear to be working correctly would seem to indicate that what has become corrupt is the identities info… You may want to try deleting your identities and see what happens before re-creating prefs.js. I don't recommend you to keep using that prefs file even if removing the identities solves the problem because, if something is corrupt there, we don't know what else could be wrong, but may be worth a try if you're curious…

Thanks again. I followed your first set of instructions (from 11:44 am) which did not fix the problem. Information is still not staying in the Account Settings fields. Trying to send a new message fails in the same way that I described previously. Not only that, but I was not able to access emails on the main account as the server information in that 2020 prefs file is out of date.

Should I revert the name changes in the prefs.js files before trying the other steps you suggested at 1:35 pm? (i.e. rename prefs.js back to prefs-1.js and prefs.bak back to prefs.js)

And how do I go about deleting the identities?

Should I revert the name changes in the prefs.js files before trying the other steps you suggested at 1:35 pm? (i.e. rename prefs.js back to prefs-1.js and prefs.bak back to prefs.js)

If you want to open Thunderbird again as it was before, either to take note of the account settings, or to remove the identities and see what happens, yes. Quit Thunderbird before renaming those files.

Otherwise, no, just stick with the instructions I provided, which are intended to have NO prefs.js file, so Thunderbird creates a new one.

And how do I go about deleting the identities?

There is a Manage Identities button in the main account settings pane where your account info disappears that lets you play with them.

EDIT: I didn't realise prefs-1.js was so old… The fact that the problem persists with a prefs file that old isn't encouraging, it would be an indication that the problem is elsewhere and not knowing where exactly you may end up having to create a new profile…

Thanks so much for this. I started afresh as you suggested so that Thunderbird would create a new prefs.js and there is definitely progress. I have set up one account, the one I use most frequently, and am able to receive and send from that one. Still working on the other 2 and running into some issues which I will report on further but just wanted to say thanks for all the support so far.

Reporting further. Information in the Account Settings fields (Your Name, Email address, Signature text, etc.) is now persisting as it should after entering, for all accounts. On two of the accounts I can send and receive. On the other (the one I use as my main email) I can send. However on this one I have new emails showing up to 11 a.m. today (before I created the new prefs.js file) but have not received anything since then. On my phone and on the webmail interface for this account new emails are coming in. It also claims to be downloading about 1450 new messages every time I open TB or click "get messages" but my total number of messages in my inbox does not increase. There are a large number of duplicate, unread copies of messages from 2023 and 2024 that were already in my inbox. I suspect this has something to do with POP vs IMAP which I must admit I've always been a little unclear about. My server for the "main" account is POP whereas the other two are IMAP.

Yeah, this is a consequence of the account being POP and setting it up anew, hence having lost track of which messages had already been downloaded and trying to download everything that's on the server again…

Do you have a lot of mail on the server there? Is setting that account as IMAP an option?

Did you set the Server Settings > Local Directory of the account to be the same you were using before as stated in the last step of the instructions I gave you? If not, do that now, but take Thunderbird offline first (File > Offline > Work Offline), restart Thunderbird, then make the change, and take Thunderbird online again.

Yes, I checked and the local directory setting is the same as it was before C:\Users\*****\AppData\Roaming\Thunderbird\Profiles\*********.default\Mail\pop.1and1.com. (1and1.com was a hosting service that I used for a long time but stopped using quite a while ago. At this point I assume that it is just an arbitrary filename and has no other significance).

The "main" account continues to load old duplicate emails and not receive new ones. I delete the duplicates from my inbox and the same ones just keep coming in.

I suppose it would make sense to switch to IMAP for this account. I try to keep the server cleaned out and leave only emails from the last couple of years on it but I have decades of old emails stored locally on my computer in TB. I just want to be sure that nothing happens to those. How do I go about switching to IMAP?

Strangely the two accounts that are working do not have the same local directory name as before. When I tried to set one to its old value \Profiles\********.default\ImapMail\imap.shaw.ca it told me "Local folder is not suitable for message storage" and it seems to have renamed itself to imap.shaw-1.ca. Likewise my gmail local directory has renamed itself from its old value imap.gmail-1.com to imap.gmail-2.com. As these are now working OK I am reluctant to make any changes to them.

At this point I assume that it is just an arbitrary filename and has no other significance

Account folders are named after the incoming mail server, with a number appended if another folder with the name already exists, but yeah, doesn't really matter how exactly they're named, if that's what you mean.

The "main" account continues to load old duplicate emails and not receive new ones. I delete the duplicates from my inbox and the same ones just keep coming in.

Go to the account Server Settings and uncheck the settings to check for and automatically download new messages if you want it to only check for new mail manually.

Thunderbird uses a popstate.dat file in the POP account folder to keep track of which messages have already been downloaded. Looks like there is a problem with that file. Re-creating it should solve the problem, but will cause all messages on the server to be downloaded again, although that cannot be worse than what's happening now.

At this point, the size of your Inbox may be growing too much and be part of the problem, though, so we'll also move that out of the account folder and into Local Folders to make Thunderbird create a new Inbox for the account:

1. Quit Thunderbird.
2. Make a backup copy of the profile folder, just in case.
3. Move Inbox (only the mbox file with no filename extension) out of the POP account folder and into Local Folders.
4. Delete Inbox.msf
5. Delete popstate.dat
6. Launch Thunderbird.

How do I go about switching to IMAP?

You just set up the account that way. Don't have to delete the POP one if you don't want to, may have both if you want.

When I tried to set one to its old value \Profiles\********.default\ImapMail\imap.shaw.ca it told me "Local folder is not suitable for message storage"

This is weird. The following article explains the meaning and the circumstances under which you might get that error message. Makes no sense to me that you would get it for that folder…

https://support.mozilla.org/kb/dangerous-directories-Thunderbird-account-settings

As these are now working OK I am reluctant to make any changes to them.

Yeah, re-creating IMAP accounts is trivial, you may leave them that way if you want.