Hello Jenny, my name is Alexander. I'm an Independent Advisor and I'm happy to assist you!
I recommend that you follow the steps below:
Open Settings - System - Notifications & actions.
Switch the button ‘Get notifications from apps and other senders’, which is under ‘Notifications’.
Then put the check for Outlook under ‘Get notifications from these senders’.
Switch off the notifications for Outlook.
Best regards,
Alexander B.