If you have selected the Inbox and set up: View > Sort by: Date, descending, unthreaded

And you do not change any of those settings and Inbox is still selected when you exit Thunderbird. When you exit Thunderbird those settings are remembered in the session.json and xulstore.json files. This means when you restart it would auto open on Inbox with those settings.

If you selected some other selection or set a filter prior to exiting then it will auto open using whatever settings were in force when you exited.

If you select any 'threads' option then you will see everything in a 'threaded' view.

If you have selected the Inbox and set up: View > Sort by: Date, descending, unthreaded

you can force all other folders to use the same. click on the far right column header icon to see drop down, go to the bottom and hover over 'Apply columns to' to see further options where you can select other folders to use same settings.

If you start Thunderbird and it opens on Inbox, but it is not displaying any unread mail, then prior to exiting you had some filter operating on that folder. Maybe 'View' > 'Sort by' > 'Read' was selected. Whilst that option can be set via the setting above, that option could also have been set by you clicking on the 'Sort by Read' column header.

If Thunderbird open on Inbox and you cannot see the unread mail, please click on the 'Sort by Read' column header to remove that filter.

Unfortunately this didn't work. I clicked on the settings recommended in the inbox. I closed thunderbird and re-opened it only to find the email from thunrderbird support with your suggested solution was hidden !

Again I clicked "view, view threads with unread" and then "view, threads all" to make it visible again

Do you have any cleanup programs working on your computer like CCleaner or WiseCleaner or even some Anti-virus products have this ability? If yes, then you need to set your Thundrebird profile folder as exempt from scanning and access.

But it is possible, for some reason, there are some files that are not being updated on exit. So try this:

1. Menu app icon > Help > More Troubleshooting Information 2. Under 'Application Basics' -profile folder - click on 'Open folder'

A new window opens showing the contents of your profile name folder.

3. Exit Thunderbird now - this is important.

4. Delete the following files:

• session.json
• xulstore.json

5. Start Thunderbird

Allow Thunderbird to check/download any mail.

Set up everything as required. Use Thunderbird for a while but do not change the setting you like using. Then exit Thunderbird, wait a short while for background processes to complete - (note you should always allow this before you shut down computer) Restart Thunderbird and see if the settings open correctly.

Thanks for the very prompt and accurate problem resolution

Good to hear all is now ok.

Thank you very much. You solved my problem! Best wishes.