Just discovered that this only applies to POP3 mailboxes. I can see my IMAP ones fine (but they're very much in the minority, sadly).

Thanks in advance for any help.

Is this forum still live?

Anyone out there can help me?

Can you be a little more specific about what's missing, or provide a specific example for one missing folder?

This sounds very much like anti-virus software did screw up Thunderbird mail files. If that's really the case then I'd hope you do have a backup of your Thunderbird profile folder created prior to the incident.

In general, it is recommended to create an exception in your anti-virus software for the Thunderbird profile folder, so that the anti-virus real-time scanner will not scan it. http://kb.mozillazine.org/Profile_folder_-_Thunderbird

Hi christ1 and many thanks for getting back to me.

I enclose screenshots of the top left of Thunderbird showing an IMAP folder working perfectly but the POP3 inbox tab just sitting there with the little wheel going round loading nothing.

I have 2 identical setups on 2 machines so I can copy over from one to the other if need be. Is that simplest?

Good idea to exclude the profile folder, will do.

Do you think the problem is the profile or the folders? Or both?

Thanks again,

Bob

I'd be more interested in a screenshot showing the troubled folder in the file system, i.e. in Windows Explorer.

Here are screenshots of the mail files. I deleted all the .msf files as I read that would solve corrupted indexes, but they haven't bee rebuilt.

Also the profile folder (or as much as will fit on one screen).

As I'm not sure what you're after, I've no idea if this is useful.

Bob

The left screenshot is more or less what I was looking for, but without context it's not very helpful. The screenshot shows 'Local Folders' with a number of subfolders, and a number of mail files, like 'Accountant' (137 MB), and 'AirBnB' (118 MB).

Are you saying you lost messages from these two folders in Thunderbird? What's odd is that the corresponding .msf files both have a size of 0 bytes. This may indicate that the mail files do no more contain mail, despite the size. Presumably when attempting to compact the folder 'Accountant' in Thunderbird, the file will end up with 0 bytes as well. You can give that a try to prove the theory.

If this is what's going to happen close Thunderbird, delete both files, Accountants, and Accountants.msf, and copy over Accounts from the other machine. Do not copy the corresponding .msf file. Start Thunderbird, and verify whether you do see mail in the 'Accountants' folder.

If that works, backup your profile folder. https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data#w_backing-up-a-profile

Hello again and many thanks for getting back to me on a Sunday. :)

My problem is that I don't know what it is that you're looking for. As I said, I must have around 100 mail folders, they're still there but Thunderbird can't find them or display them. I get the little wheel going round but no messages. I simply sent a screenshot of the first few.

I tried compacting 'Accountant' but nothing happened. The file is the same size as before.

If you tell me exactly what it is you'd like a screenshot of, I'll do it. But I think at this point I need to copy over the profile. Am I right?

Before anything else try to start Windows in safe mode with networking enabled. - Win10 https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode

Still in Windows safe mode, start Thunderbird in safe mode. - https://support.mozilla.org/kb/safe-mode

Does the problem go away?

Brilliant!! You're a star!! They're all back!!

So can I restart Windows normally now? This low resolution is doing in my eyes! :)

Windows safe mode disables anti-virus software, so Bitdefender is most likely the culprit. Below are some general suggestions to avoid these kind of problems. Beyond that you'd need to check with Bitdefender support.

Create an exception in your anti-virus software for the Thunderbird profile folder, so that the anti-virus real-time scanner will not scan it. http://kb.mozillazine.org/Profile_folder_-_Thunderbird

Don't let your anti-virus software scan incoming and outgoing messages.

Don't let your anti-virus software scan attachments.

Don't let your anti-virus software intercept your secure connection to the server.

Remove any add-ons your anti-virus software may have installed in Thunderbird.

Keep it working. http://kb.mozillazine.org/Keep_it_working_-_Thunderbird

And last but not least, backup your Thunderbird profile on a regular basis. https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data#w_backing-up-a-profile

Many many thanks for sorting this. :)

I've excluded the profile folder as you suggested and also outgoing mail. I'm reluctant to exclude incoming mail and attachments as that seems contrary to what the antivirus is there for in the first place.

Thanks again, excellent service! :D