Check under View / Folders that you have all marked (or unified if you use that)

Yes, the View/Folders All button is checked. It doesn't make a difference.

If you used the 'Shift' key to select emails then you must have selected a contiguous block of emails. eg: Click on first email, hold down shift key and click on last email and all emails in between become highlighted. clicking on delete would then mark all of those highlighted emails as deleted. They would be hidden from view and should reappear in the Trash/deleted folder.

You can immediately undo this action: 'Edit' > 'Undo delete message'

If emails are in 'Trash/Deleted' folder move them back.

However, if all emails disappeared, then either all were selected or there is some corruption in that folder. DO NOT compact that folder.

In thunderbird

• Help > TRoublshooting Information
• click on 'show folder' button

a new window opens showing profile folder name

• Close Thunderbird now - this is important

you should see 'Mail' and possibly 'ImapMail' folders

• IF POP account: click on 'Mail' folder
• click on mail account name

you should see the 'Inbox' mbox file - it has no extension.

• Open the 'Inbox' file using Notepad

Each email will start with these lines: this is an example

• From - Sun Dec 28 18:14:40 2014
• X-Mozilla-Status: 0001
• X-Mozilla-Status2: 00800000

Use 'Edit' > 'Find' Starting at the top use the look for this line: X-Mozilla-Status: 0001

Make sure each X-Mozilla-Status: has the number 0001

• edit the number as required working down through the document.
• Save the file.
• delete the 'Inbox.msf' file. A new one will be auto created.
• Restart Thunderbird.

that should get emails back in Thunderbird Inbox Report back on whether this worked.

Once you have the emails back do this:

• Move all good emails into another suitable folder for storing.
• Delete everything you do not want.

When Inbox is empty:

• right click on 'Inbox and select 'Compact'.

This should clear up the Inbox.

Many thanks for this detailed answer Toad-Hall. Half-way through trying this I realised it was a slightly different problem; ie., I can retrieve the emails in the folder by simply closing down Thunderbird and restarting it. So I don't have to go hunting for them as though the folder were corrupt. It seems rather, to be a problem with the +SHIFT key select function and now the Search function again. The pane of emails in the inbox become inaccessible once I activate either of these functions. The emails don't 'disappear' because everything goes back to normal once I've restarted Thunderbird. But it's time-wasting to have to restart Thunderbird every time I use these functions. Hope I've made myself a little clearer.

Ah! But were you finding messages with other than the required 0001 value?

Using Shift select and delete will mark messages as deleted, but it does not actually delete them from the file. If there is corruption, TB will have difficulty working out what is marked as deletd and what is not, ultimately you could lose emails. Obviously, this will effect what you see and what you search. You need to rule out the possibility of a corrupt folder as this will impact on everything.

Please follow the instructions exactly as detailed and then report back on the results. This should resolve the issue if there is corruption in that folder.

If it does not fix the issue, then at least we can proceed knowing the file is ok.

I followed these instructions and the same problem remains. I don't think it's a corrupt file issue. Whenever I carry out a search emails function or try to delete multiple emails, I'm left with an empty pane below, and all my emails visible above. When I click on any of these emails above, they do not open. When I click on a searched and found email, while the date and folder are visible, it does not open. So while the emails themselves are visible, they stubbornly refuse to be opened. At this stage, I'm just rebooting Thunderbird every time which solves the problem. It's just tedious to have to keep rebooting Thunderbird every time I want to search in my emails and/or delete multiple emails.

Perhaps this is something in the preferences which is not updating correctly. Start by deleting the specified files and folders to see if this resolves the issue.

In thunderbird

• Help > TRoublshooting Information
• click on 'show folder' button

a new window opens showing profile folder name

• Close Thunderbird now - this is important

Look for and delete the following files:

• global-messages-db.sqlite
• panacea.dat
• session.json
• xulstore.json

• Click on 'Mail' for pop mail accounts
• If you have used 'Unified' view, there will be a 'smart mailboxes' folder
• delete this folder: 'smart mailboxes'

These files will be recreated afresh when you start Thunderbird. Smart mailboxes will be recreated when and if you ever use 'Unified' view.

• Close window - top right X
• Restart Thunderbird.

Please report back on results.

Thanks for your effort. I have two email addresses with my Thunderbird account, which I've had for many years. Both of these are therefore fairly bloated. I don't know if this is an issue but I don't think so. As an experiment, I tried all those steps you listed above for one of the inbox folders. When I went back in and tried using the shift key again to see if the problem remained in that folder, it did. All of this only happened after the last Thunderbird update. Before that, everything worked perfectly. I've pretty much given up on fixing this and am thinking of migrating everything to gmail, much as my Thunderbird account has served me so well until now.

Can you just confirm something for me as I'm a bit confused. How do you have bloated Inboxes?

If you had followed my first set of instructions...... quote:

• Move all good emails into another suitable folder for storing.
• Delete everything you do not want.
• When Inbox is empty: right click on 'Inbox and select 'Compact'.

......you should have a completely empty Inbox which would only have received the most recent couple of days of emails, but in your last comment you say: I have two email addresses with my Thunderbird account, which I've had for many years. Both of these are therefore fairly bloated.

Did you move all of the good emails out of Inbox and put them in another folder and then delete all the unwanted emails? At this point that Inbox folder should be empty and then finally compact the Inbox folder. This should have left you with a fresh Inbox and now maybe only the recent few days of emails in it at the most. So how are you're Inboxes still bloated?

Yep, this last response from me was after I did all of that. What I was trying to express in that response was my thought that maybe the procedure did not work because: 1. I only did this for the current inbox on one of the accounts ie., should I have done it for both accounts. 2. There are still quite a few years' worth of emails stored in other folders in those accounts. Is this bloating somehow also a factor. Thank you