Not good news I'm afraid.

Some background info to help explain: Emails are downloaded and stored in an mbox file, which is a text document. The emails are written, one after the other, to the mbox file in the order downloaded. When you choose to delete an email, it is 'marked as deleted', it is still in the file, but hidden. This facilitates the ability to undo a deleted message. So if you have several emails that are 'marked as deleted', it is like a long text document with various sections ear marked for complete removal. When you compact the folder, it removes all those 'marked as deleted' emails.

The 'Inbox' and 'Junk' folders usually see a lot more activity than other folders. So, they should be compacted on a more regular basis than other folders. I'll delete several emails each day and therefore will empty junk and compact both Inbox and Junk on a daily basis.

It is also advisable to use the Inbox as an Inbox for incoming messages and not as a general store for good emails.

However, if the file has become corrupted at some point, compacting can have a negative effect. This has unfortunately occurred in your case.

Frequent compacting is a way of maintaining files. So, perhaps you do not compact the Inbox on a regular basis?

Backup: If you keep a backup then it may be useful in retrieving some emails.

If this occurred to a POP mail account Inbox and your account Settings choose to keep a copy of messages on server, try this to see if you redownload emails.

In Thunderbird Help > Troubleshooting Information click on 'Show folder'

a new window opens showing contents of your profile folder name.

Close thunderbird now - this is important

click on 'Mail' folder click on 'mail account name' look for and delete this file: popstate.dat

It keeps a record of what has been downloaded from server to stop it downloading it again.

close window - top right X Start Thunderbird.

It should start to get messages from server. If there was anything left in the server Inbox, it should create a new 'popstate.dat' file and download them again.

If this was a Pop gmail account, then gmail also keeps a record of what you downloaded. To download them again, you can reset POP in Gmail to "Enable download for all messages" to download all messages again. There is a 'recent mode' method allowing the redownlaod of emails. See info :

• https://support.google.com/mail/answer/47948?hl=en

general info to help maintain healthy Thunderbird.

• http://kb.mozillazine.org/Thunderbird_:_Tips_:_Compacting_Folders
• http://kb.mozillazine.org/Keep_it_working_%28Thunderbird%29

Hi Toad-Hall,

Thanks a bunch for getting back, and the advice. Afraid your top line gloom was correct. Never happened to me before and I've been using TB since the getgo about 20 years ago.

Also deleted the popstate.dat file you suggested but it failed to download the message from the server, even though there are about 100 messages still there. There is no new postate.dat file either. Maybe I'm doing something wrong.

I do have another fairly updated Inbox on another machine. is it possible to import that Inbox into this one ?

Thunderbird had to be closed first. then delete the popstate.dat file then restart Thunderbird.

Please check you fully exited Thunderbird before deleting the file.

then restart Thunderbird. Usually upon starting up, Thunderbird will check for messages on server. Otherwise click on 'get Messages'.

Thanks TH ! bingo. right on the money - it worked. Also saved a problem I had with hotmail for a while which caused it to crash on loading.

Any possibility to import the Inbox from another machine ?

re :import the Inbox from another machine

If the other machine uses Thunderbird and you are refering to an Inbox in a thunderbird profile folder:

Manually OR use an addon tool methods described below.

Manual: OLD machine: In Thunderbird

• Help > Troubleshooting Information
• click on 'Show folder'

• Close thunderbird now - this is important

• click on 'Mail' folder
• click on 'mail account name'

look for an mbox file called 'Inbox' - no extension (not Inbox.msf) copy paste this file to an external device eg: USB memory stick.

Rename that file to eg: Oldinbox

On New computer: In Thunderbird

• Help > Troubleshooting Information
• click on 'Show folder'

• Close thunderbird now - this is important

• click on 'Mail' folder
• click on 'Local Folders' mail account
• paste the renamed 'OldInbox' mbox file into 'Local Folders' folder.

Start Thunderbird.

Using an addon tool: Download and install this addon 'ImportExporttools' onto both computers;

• https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/

How to Install Add-on Extension: After downloading addon extension *.xpi file to desktop or downloads folder.

n Thunderbird 'Tools' > 'Add-ons' or 'Menu icon' > 'Add-ons'

• Click on gear wheel icon and select 'Install Add-on From File'.
• Locate the *.xpi file you downloaded and click on 'Open'.
• You will need to restart Thunderbird when prompted.

On old computer right click on 'Inbox' and select: 'ImportExporttools' > 'Export folder' choose where to save it by selecting a folder and click on 'Select folder' button.

then access that saved file and rename it to 'OldInbox'

On new computer; right click on 'Local Folders' mail account and select; 'ImportExporttools' > 'Import mbox file' select 'Import directly one or more mbox files' click on OK

locate the renamed 'OldInbox' mbox file you exported and click on Open.

I'm very grateful for your help Toad-Hall !

I just remembered another backup tool which can be very helpful & useful if you use it on a regular basis. A little program/application called "Mozbackup" which allows you to fully back up all features, subfolders, contacts, etc. in both FF & TB. Also using a USB memory stick you can restore the entire setup on another machine. You might want to mention that in other solutions.

Cheers !