So go ahead, skip the disk utility part if you're unsure what to do about it, because at this point I'm pretty sure nothing happened there and you just managed to confuse all of us, LOL. The sooner you stop downloading mail into what seems could be a corrupt Inbox, the better…

DavidGG, Thank you again. I have followed steps 1-3 of your procedure of 2/18/25 at 6.58 PM. I created the new Local Folder, POP Mail 2025-02-20, and checked (see my first screenshot) that the new folder title appeared under Local Folders. I quit Thunderbird, and made a back up copy of the profile. On the way to your step 4, I looked in the Local Folders in the Profile to check that the new POP Mail 2025-02-20.sbd folder had indeed been generated (as required by your step 5). It hasn't. Thunderbird has created a FILE with that title, and an accompanying .msf file, not a FOLDER as your procedure specifies. My second attached screenshot refers. So I have stopped at this point. (I have not yet done step 4 - renaming the mail.salight.co.uk). I would welcome your further guidance. What do I need to do to persuade Thunderbird to create an .sbd FOLDER rather than a FILE of that name? I remain enormously grateful for your and your colleagues help. Iain

Ah, right, my bad, sorry. The .sbd folder would only appear as a result of creating a subfolder in Thunderbird. So you may do that in Thunderbird (create a dummy subfolder of POP Mail 2025-02-20, then quit Thunderbird), or you may manually create the .sbd folder in the filesystem (with Thunderbird not running). You may then proceed from there.

DavidGG. Many thanks. Thunderbird has created the new Inbox, and downloaded the Inbox off the server (227 messages). It has not downloaded any Sent items, but maybe they are not retained on the server? It has not picked up the files from the POPMail2025-02-20.sbd folder. This is a matter of concern. I understand that this could be due to corruption, but something else has happened that is surely not right, and may also be the cause. I will detail exactly what I did. I started in the Thunderbird Inbox window, deleting from Local Folders the POP Mail 2025-02-20 folder created previously, because I noted that all the other folder names did not contain spaces and I thought this might matter. I then created a replacement new folder POPMail2025-02-20, and under that a sub-folder with the same name. Though I didn't think to screenshot it, those folder names were there in the panel on the left hand side of the Inbox window when I quit Thunderbird. I then went to the file structure and checked that the POPMail2025-02-20.spd folder had been created under Local Folders (your Step 5). Further down local folders were two new files POPMail2025-02-20 and a corresponding .msf file. At the time I mistakenly believed that they related to the original local folder I had created (and deleted) so I deleted them. I then renamed the POP account folder in accordance with your Step 4, and started to copy (not move - I wasn't keen to delete things) the Inbox, Sent, etc files from the renamed account into the POPMail2025-02-20.spd folder (your step 6). When I opened that folder (which I expected to be empty) I noted that there were another two files POPMail2025-02-20 and the corresponding .msf file. I left them alone. At this point I spotted the pattern that Thunderbird creates these files as a result of a new Local Folder being set up, and that the two I had deleted from Local Folders had been created by this mechanism second time around, rather than relating to my original Local Folder POP Mail 2025-02-20. I then launched Thunderbird. The Inbox window came up and downloading from the server started. At this point I noticed that, under Local Folders in this view, the POPMail2025-02-20 folder and its subfolder of the same name, which I had created, were not there. They were when I previously quit Thunderbird. Can this be why Thunderbird has not picked up the contents of the .spd folder. I attach 3 relevant screenshots. Help Please! I am very keen to undo whatever has to be undone and to repeat the process, or to try another route to get Thunderbird to make these files visible. As ever, thank you. Iain

@iwright2: In your screen shot with the contents of Local Folders I see that an mbox file named POPMail2025-02-20 accompanying the POPMail2025-02-20.sbd folder is missing. Without this file TB cannot display the folder POPMail2025-02-20 and its sub-folders in your Local Folders in the Folder pane. Create an empty file in a text editor, name it POPMail2025-02-20, delete the extension .txt your system will add to the file name and - TB closed - paste the newly created file in ...\Mail\Local Folders\.... in the TB profil folder. Restart TB and verify your Local Folders, in particular the folder POPMail2025-02-20 and its subfolders.

It has not downloaded any Sent items, but maybe they are not retained on the server?

Rather than not being retained on the server, it's that POP can only see Inbox on the server. To see any other folder that may exist on the server, you have to set up the account as IMAP or use webmail.

It has not picked up the files from the POPMail2025-02-20.sbd folder. This is a matter of concern.

Not yet. You misunderstood the instructions. We have to fix that now.

deleting from Local Folders the POP Mail 2025-02-20 folder created previously, because I noted that all the other folder names did not contain spaces and I thought this might matter. I then created a replacement new folder POPMail2025-02-20

This wasn't necessary, spaces in the name aren't a problem, but nothing wrong with choosing a different name if you want either.

and under that a sub-folder with the same name.

This is wrong. I gave you two mutually exclusive options:

• Create a dummy subfolder in Thunderbird, i.e. a subfolder with any name and no purpose, just to make Thunderbird (not you) create the corresponding .sbd folder for the parent folder in the filesystem.
• Create the .sbd folder in the filesystem yourself.

Although the name you chose should in principle have served the same purpose (as I said, it could be named anyway you want), choosing that name seems to have caused you some confusion and the folder hierarchy is messed up now.

checked that the POPMail2025-02-20.spd folder had been created under Local Folders

It's .sbd, not .spd, but I suppose this is just a typo you made when posting, because the folders appear to have the right suffix in the screenshots.

Further down local folders were two new files POPMail2025-02-20 and a corresponding .msf file. At the time I mistakenly believed that they related to the original local folder I had created (and deleted) so I deleted them.

Actually, that assumption was almost correct, and this is where everything seems to have become messed up.

For each folder you create in Thunderbird, an mbox and the accompanying .msf file will be created to store messages in that folder, and then also a .sbd folder if you create subfolders under it.

Those files without spaces in the name would be related to the new folder without spaces in the name that you created, not to the folder with spaces in the name that you created at first. The files with spaces would have been automatically deleted by Thunderbird when you deleted the corresponding folder in Thunderbird, so it would seem that at this point you deleted the files associated with the folder you created in Thunderbird without spaces in the name… EXCEPT for the fact that…

[…] POPMail2025-02-20.spd folder (your step 6). When I opened that folder (which I expected to be empty) I noted that there were another two files POPMail2025-02-20 and the corresponding .msf file.

The folder should have been empty, but it looks like somehow you moved there the two files you say you had deleted… And it's the absence of these files in the right place that's causing Thunderbird to not show the whole folder hierarchy… Thunderbird isn't looking into POPMail2025-02-20.sbd (or maybe it's looking there but not showing what it finds), because the absence of the mbox file makes it not show the parent folder POPMail2025-02-20 in the folder pane in the first place.

the two I had deleted from Local Folders had been created by this mechanism second time around, rather than relating to my original Local Folder POP Mail 2025-02-20

Exactly.

under Local Folders in this view, the POPMail2025-02-20 folder and its subfolder of the same name, which I had created, were not there.

The folders will appear in Thunderbird when you fix what you have now, regardless of whether the mbox files are corrupt. If there is a corruption problem, it will manifest in not all the messages appearing, but the folders themselves will:

1. Quit Thunderbird if it's running.
2. Move POPMail2025-02-20 and POPMail2025-02-20.msf out of the .sbd folder, one level up, into Local Folders, so they appear at the same level as the corresponding POPMail2025-02-20.sbd folder.
3. Launch Thunderbird.

That's it. As a result of doing that, Thunderbird should now display POPMail2025-02-20 in the folder pane (because it can now see the associated mbox file), and that in turn should make the other folders appear as subfolders of it.

DavidGG, (and Mapenzi), THANK YOU!! All the 'missing' folders and their contents have seemingly now returned under the correct headings in the folder pane (just as you said/hoped they would). So seemingly no corruption. One is just left wondering what went wrong in the first place.... I struggle with words to express my gratitude, not just for fixing my problem, but for the precisely detailed, enduring, and patient manner of your assistance. I have not had to do anything like this before, and am of the generation which was not brought up on computers (or calculators - did school exams with a slide rule!). I just feel awkward that there is seemingly no way I can compensate you for the time you have spent. But I am grateful beyond words. A fantastic service. Thank you again. Iain

Glad to know. See all those popstate.dat files in the old POP account folder? popstate.dat is the file that Thunderbird uses for POP accounts to keep track of things like which messages have already been downloaded. There should be a single popstate.dat file there, but you had multiple of them, which would indicate Thunderbird was choking on something there. The problem was probably a combination of that and Inbox starting to become too big.

Again a helpful insight, for which I again thank you. I will seek to manage/file email in a better disciplined way in future. I know it is not necessarily how others do it, and it may be how my brain works, but because use email to transmit or transact fact, rather than idle chat, the historical email trail is for me a record of past events or commitments, which has been a hugely helpful reference on many occasions. What is the best/simplest way to back this stuff up? I don't want to have to file individual emails in individual folders. Too time consuming. Many thanks and Best wishes again, Iain

You may create folders under Local Folders, to store and organise your mail locally on your computer there however you wish, independently of any mail account you may have.

You may also want to use Thunderbird's Archive feature:

https://support.mozilla.org/kb/archived-messages