I have noticed this behaviour in Mail App.
I have noticed that this erratic behaviour is also happening in Whatsapp notifications.
All the WhatsApp notifications disappear from the Notification centre, the moment Whatsapp is opened even if it is immediately closed without touching/ opening any chat.
This occurred in all regular releases iOS 10.2.1, 10.3, 10.3.1.
This also occurred in all their betas.
[doublepost=1491326766][/doublepost]Do you have any updates from Apple in this regard.
It does that with some apps. Mail, Facebook, WhatsApp, etc but not others twitter, messages, Apple News, etc. it's very weird. Mainly noticed it post iOS 9 when Apple decided to remove notifications being "sorted by app" instead of "recent" as we have now.
[doublepost=1491370666][/doublepost]
So I just tested again and now my mail notifications only would populate in Notification Center when I've opened the mail app. This is opposite of uandme72's behavior. Faith is diminishing.
Could this be because the mail app is showing brand new emails that it just downloaded/updated? (vs uandme72 having downloaded mail cleared out of Notification Center)