Duplicate new email notification on 2nd PC - also already read email on 1st PC

I have Outlook opened on 2 different PCs because of Laptop and Office-PC.

When I get new Email then Outlook shows new email notification icon in Windows taskbar - that is good.

When I read new Email then email notification disappears again - that is good.

Now I switch to my other PC and there I still see new email notification - that is bad.