How big (in GB) is the Inbox folder and how many messages does it contain? R-click > Properties > Number of messages & Size on disk

Hi and Thanks for the prompt response. R-click > Properties > Number of messages & Size on disk: Both report "Unknown".

Is the Inbox folder in a POP or an IMAP account? Anyhow, TB shut down navigate to your Thunderbird profile folder as described in this SUMO article https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_finding-your-profile-without-opening-thunderbird Note the size of the profile folder abcd1234.default-release (or some similar name) If POP account go to folder Mail > pop.xxx.xx and note the size of the Inbox file (the one without an extension) If IMAP account go to folder ImapMail > imap.xxx.xx and note the size of the INBOX file

Thanks for the info for corrective actions. It is a POP3 server and I will try the directions above and will let you know the outcome.

Hi, Inbox folder size is 6.3 Gb

6.3 GB is too big a size for an Inbox folder - respectively the correspondant Inbox mailbox file in the TB profile ! This is the folder which suffers most of the message traffic and therefore most likely can get damaged. Ideally its size should turn around some hundred MB and to maintain a rather small size one should delete messages without importance and archive messages one wants to keep- or has to keep for legal reasons.

I prescribe a weight loss diet for your Inbox folder. Delete as many messages as you can and archive most of the rest, e. g. in the Local Folders by creating thematic folders. When this is done compact the Inbox via R-click > Compact ...

After deleting all unnecessary messages you may compact the Inbox a first time and test whether TB still freezes (gets unresponsive). If TB is revived you may take more time to set up an archive for your important messages later when it suits you.

Thank you. How do I access the contents of the Inbox folder? TB won't load it and it crashes the program when I try. Is there a utility program to access and edit the contents?

Thank you. How do I access the contents of the Inbox folder? TB won't load it and it crashes the program when I try.

OK, we must change our strategy. Does TB crash immediately on startup? As long as TB is still responsive go to Settings > General > Disk Space: click on "Clear Now", then go to Indexing and uncheck "Enable Global Search and Indexer".

If this doesn't work, open the TB profile folder following this description https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_finding-your-profile-without-opening-thunderbird In the profile folder search for rhe file global-messages-db.sqlite and delete it. Then open the subfolder "Mail", open the account folder pop.xxx.xx and delete the file Inbox.msf. On restart TB will take some time to rebuild the Inbox.msf and the global-messages-db.sqlite files (you can follow progress in the left corner of the status bar).

If TB still hangs, force-quit the application. Go again to the Profile folder > Mail > pop.xxx.xx, rename the big Inbox file to Inbox-1 and delete the Inbox.msf file. This manipulation neutralizes the big Inbox and and on restart forces Thunderbird to create a new Inbox which will download the messages still being on the server!

By this manipulation at least you should get a Thunderbird which no longer becomes unresponsive. But there still is the fate of the big Inbox which seems to be damaged and the question how to recover all the messages stored in it. [If you had a Mac or Linux PC it would be easy to cut the big Inbox file into smaller Mbox files of 1 GB or 500 MB each by a simple command line in the Terminal] There are Mbox-Breaker tools in the Internet, some free for smaller files or paying for big GB files. I can't test them because I have a Mac.

You could also open the big Inbox file in a text editor and cut it manually in two or three or more smaller mbox files (copy & paste method). For this manipulation you need to download a very strong text editor since the usual Windows editors are too weak.

Regard the crash - do you get a crash report dialog?

Also. start Windows in safe mode with networking enabled - https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode. Are you able to access the Inbox?