It might be that you just have a broken MSF (Index file)

With Thunderbird closed go to C:\Users\YourUser\AppData\Roaming\Thunderbird\Profiles\YourProfile\

Then ImapMail or Mail depending on your e-mail configuration and then search the folder where these messages are.

You'll find a pair of files for each folder FolderName FolderName.msf

Delete the MSF file, and start TB, see if it fixes that.

Thanks for the try, but it doesn't work. A new MSF file is produced on restart, but my messages are still mainly missing

Can you open the file with no extension in Notepad++, Wordpad or another editor and see inside it?

It is a text file, not rocket science. See if you can find text and part of the lost e-mails. If you can, then the data is there and you are just having an issue with TB.

If nothing is there then you are quite f* up. (Unless you can recover those messages from the Trash in your e-mail server, don't loose that chance).

Thanks again, but no. I have virtually nothing to use (see screen shot). TB has tried to do the transfer but has somehow failed part way through. I have tried every other possibility I can think of (trash; archive; general search). All negative. Looks like they've gone for good ? Any ideas on what may have happened and how I can stop it in the future?

re :Regrettably only parts of the INbox messages arrived in the storage area. Regarding original Inbox email location: You mention 'Inbox', but are you talking about a POP mail account Inbox or an IMAP mail account Inbox or 'Local Folders' Inbox?

What storage area? They were in Inbox, but where did you try to move them to? Another folder in the same mail account? Are you talking about moving them into 'Local Folders' mail account?

In your Profile folder name: 'Help' > 'Troubleshooting Information' click on 'Open Folder' button a new window opens showing contents of Profile name folder. if POP or Local Folders click on 'Mail' OR if imap mail account click on 'ImapMail'

click on mail account name make sure size column is showing post image showing contents of mail account folder. If moved to another folder in same mail account, what folder name did you move them into?

if you moved them into Local Folders mail account: locate Local Folders mail account make sure size column is showing post image showing contents.

INbox is IMAP mail account. Tried to move messages from INbox to Local Folders - folder name "Foyer recd 2017". I attach image showing contents of the appropriate Local Folder opened via Profile as you ask. You can see that "Foyer sent 2017" is well populated - everything transferred perfectly into this folder. Foyer "recd" 2017 should show a greater size (bear in mind that this folder was already populated with 4 messages transferred successfully on a previous date).

gas1126 please take note of what I've asked you and Toad-Hall extended the explanation. We want to know what is in a "File Folder" level not what do you see in Thunderbird.

Go to My Computer C: Drive Users folder YourUserName folder AppData folder Roaming folder Thunderbird folder Profiles folder <weird_named> folder ImapMail folder <another_folder>

Find the file Inbox (no extension) and open it with a Text Editor, be it Windows Notepad or Wordpad, I recommend something better like Notepad++

This is a file that contains a lot of emails chained one after the other, try and find if you can see the messages you've lost (in between what you will consider garbage that is a lot of internal information that goes on with e-mail exchange)

If you can find them there, or in the other new folder where you moved them, there is hope that you can recover the e-mails

As I've said before, do not forget to go check the Trash of your Gmail, Hotmail or whatever your e-mail provider is, since you can get a copy of them from that place instead of all this mess.

Thanks for the ongoing help - sorry I misread the instructions! I think I have now done what you suggest and have found a total of 17 INBOX files (no extension) in folders named: imap-mail.outlook-(number 1 - 17).com. (I have 6 active Hotmail accounts). I have opened each with Notepad. They are difficult in the extreme to make sense of (as you rightly say) but it does seem that one or two have words in there that may originate from my missing messages. Are you in a position to say how i can extract these messages in a readable form? Thanks again.

you have 17 accounts (or 16 if we do not count the Local Folders of Thunderbird if you do have 17 ""Inbox"" files, While you have only 6 accounts. When you delete accounts the folders and files are retained, not erased, so those other 11 might be from older accounts you have or you have had other issues.

If they are Hotmail, then why you don't log in to Hotmail.com and try to recover the e-mails from there? They even have a way to recover things that you already erased from the Deleted folder.

See attachment.

If not:

Order the Inbox file by modification date. All those modified recently might contain information. Those that have not changed in a month or more are easily discarded.

Then use the Find feature of any Text Editor and find keywords in the e-mail messages, like the name of the person you were greeting.

It will go straight to the part of the e-mail message you were exchanging with that person.

Then move up/down until you find the beggining and end of the message, copy it, and you have a copy of the e-mail (at least as a text file)

If you have that maybe someone here might help you recover "the folder" itself.