I may have never noticed this in Windows 10 but after the 1607 anniversary update was released I noticed that Mail notifications that turned on the Action Center Icon and the Email subject and sender information in the action center, over time, would disappear without any intervention on my part. To be clear an email notification would arrive and the Action Center Icon would change to indicated that a notification was received and the details of that notification were listed in the action center but (A) I did not click on the action center icon (B) I did not open the built-in Mail application and (C) I did not open Outlook 2010. However, after being absent from my PC for a period of time, I noticed that the action center icon was no longer showing a notification and when I did finally open the action center there were no notifications there either. What I seem to remember was that prior to the 1607 anniversary update, if you clicked on the action center icon the icon would remove the notification highlighting but to actually remove the notifications themselves from the action center I had to either clear the individual notification or clear all notification or open Outlook 2010 and download my mail.

So, is this the behavior that others are seeing? If so, is there a way to control this so notifications simply don't disappear on their own?