I would reset the shortcut icon on desktop back - Properties/Run = Normal Window

Maybe there 's more than one shortcut and Windows is confused Try this:

• On Windows Start menu - locate Thunderbird.
• Right-click it and select 'More' > 'Open file location'. ...
• Right-click on the Thunderbird shortcut and click on 'Properties'.
• Run: dropdown - select 'Normal Window'
• Click on 'Apply'
• click on 'OK'.

Thanks for the reply. It makes no difference - it opens minimised with “Normal window” selected

Try this:

In Thunderbird

• Menu icon > Help > More Troubleshooting Information
• Under 'Application Basics' - half way - Profile Folders - click on 'Open Folder'

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

• Exit Thunderbird now.

Delete these files:

• session.json
• xulstore.json

Start Thunderbird.

Hi TH, No that had no effect on the self-minimisation, but it did wipe out my customised toolbar (now restored) and my combined inbox - can't remember how to get this back

Got my unified inbox back and have just discovered how to put a space at either end of my customised toolbar

You might want to try setting Thunderbird how you like it maximized or whatever and using the file menu to exit the program. (press ALt+F and then select exit from the menu)

I saw some issues years ago where how you closed Thunderbird affected how it opened next time (including opening two windows) If my faulty memory serves the file menu exit executes different code to clicking the X or pressing ALt+F4

Hi Matt, Unfortunately, that didn't work. I'd think of uninstalling and reinstalling, but it takes me so long to get it back to normal, with several email accounts and customised toolbar

I have a very embarrassing confession to make - I seem to have installed an add-on that is meant to do this! Very sorry :-((