Using Classic Outlook on Windows for personal email, calendar, and contact management
I am having the same issue. Came here to discover it is widespread.
Clicking on the notification DOES open the email, but it opens it behind other windows. So I can't see it, can't tell it has been opened, and the email is marked as "read".
I've turned pop-up notifications on for a reason - to respond quickly to certain emails. Opening the email "invisibly" does not meet that need.
Microsoft, this is worse than no pop-ups at all.