Just to precise the file Inbox before upgrade has had a bigger size(more than 6 GB). Now this file has got 4,2 Gb.

4.2Gb sounds like the limit for 32-bit Thunderbird. Did you previously use a 64-bit build?

I have 64bit Windows 7. Actually, it seems like after upgrade TB has cut the Inbox file by reducing the correspondence for the latest 8 months and bringing it to the limit of 4Gb. Do you have any ideas?

I am not sure which was one used previously but today it has been upgraded to 52.9.0 (32-bit): Version 52.9.0 User Agent Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.0

I could restore the file with R-studio recovery but i couldn't because the file Inbox itself was not deleted and it recovers me the one which has been changed already but not original one.

Do you know someone from Mozzilla who can help in this situation? How can I restore 6 months correspondence?

Why you keep all those emails in one simple text file document. It is difficult to find text editors that can open text files of large size. It may also be difficult to Compact that file to remove any 'marked as deleted' emails to recover space and maintain the file. Advise you create some folders and move emails out of Inbox into suitably named folders for storage in smaller file sizes. Much less risky.

If you have the option to use Windows Search then maybe there is an 'Inbox.mozmsg' folder with some old emails ?

• Access your 'profile name' folder
• click on 'Mail' folder for pop mail accounts.
• click on pop mail account name folder.
• In Profile mail account folder, do you have an 'Inbox.mozmsg' folder ?

If yes:

• Exit Thunderbird
• Copy the 'Inbox.mozmsg' folder to desktop.
• open the opied to desktop 'Inbox.mozmsg; folder and you should see a load of separate emails with *.wdseml extensions.
• Change .wdseml to say .eml.

You can open a .eml email using Thunderbird. You need to ascertain which ones you need to import.

Then start Thunderbird Use this addon extension : ImportExportTools to import .eml messages into a folder and I would recommend you do not import them into Inbox.

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

Thx mate. I will be more cautious in future but now I need to restore inbox for 6 months. I have tried a couple of hdd recovery applications but all of them restore the existing file which does not contain deleted letters. The crash has happenned immediately after upgrade of the latest version of TB.