"turned off "Badges" in the Settings, Personalisation, Taskbar and the notification number 1 has therefore disappeared"
This worked to fix it, turning Badges off and on has it back to working normal again, thanks a lot!


Keeping Up said:
None of these work for me.

I have unlinked and then re-linked the inboxes. I have opened a message in a new window and closed it again. I have removed the inbox from Favourites and then replaced it. All the while opening and closing Mail too.

The counter on the taskbar icon seems to be resolutely stuck at "1" unread message. It doesn't disappear when I have no unread messages, and it doesn't increase when I have more than 1 message. It stays at "1" even when Mail is closed.

Has anyone found a proper cure yet?

ETA: I have turned off "Badges" in the Settings, Personalisation, Taskbar and the notification number 1 has therefore disappeared. I guess that means the correct term for it is a "Badge"