If you wish to turn off the desktop notifications every time a new email arrives in your Outlook 2016 or Outlook 2013 mailbox please follow these instructions.
Whilst Outlook is Open Click on the File Tab (top left)
From the left hand side bar click on Options
A new Options window will now open up. Click on the Mail Tab (left hand side)
Scroll down the right hand side and uncheck the box which says Display a desktop alert under Message Arrival
Click on OK