I understand your issue - it does sound annoying and it is not correct. I'm wondering if this was caused by an incoming mail which went to junk or whether you have an unread email which is hidden from view. Maybe it was set as ignore thread.

Please confirm Junk/Spam folder is empty. Otherwise - right click on Junk/Spam folder and select 'Empty Junk' Then compact the Junk/Spam folder. right click on Junk/Spam folder and select 'Compact'

Do you compact your Inbox, Drafts and Junk/Spam folders on a regular basis ? If you have not done it recently please compact your folders.

Check to see if you have any ignored threads. Via 'Menu Bar' toolbar (not via 'Menu app' icon) View > Threads > select 'ignored threads' ignored threads will display a red circle with line through in the 'threads' column header - it has tooltip which says 'display message threads'.

HI Toad-Hall--

Thanks for in-depth answer and suggestions. I will try them all and report the results.

Hi again...

Thanks again for your comments/answer. I never quite found the unread mail, and don't know for sure that that is the problem, but I think I understand what's going on.

Are you familiar with the "Unsubscribe" option? It shows up when you right-click on the account name. It is NOT in the normal SETTINGS menu. It allows you to hide folders that are included in the IMAP account's list of non-deletable folders. So they're still present in the IMAP account, but they are not shown in Thunderbird.

I love this feature and have used it to get rid of all the folders I don't want to see. Even if I can get rid of only one/two/three folders per account, that significantly reduces my left-pane list of folders because I have eight email accounts.

So I think what is happening is that one of the un-subscribed folders on one of my accounts has some unread messages in it, and that's why the red dot is showing up on the T-bird icon on the start menu. At least that's the theory that I'm going with.

Thanks again for your comments. They led me to discover what I believe is the cause. I can't find the offending folder(s) because there are too many to look through, but at least I've got a good theory. And as I said in the first message, I can live with red dot.

Cheers...