By default outlook displays a notification when you receive an email. As teachers we often don't want this since it will show students the title of our emails as we are connected to a projector. Here's how to turn that off.
Open the Outlook Program
Click File, then Options
Scroll down to "Message arrival" pane and uncheck "Display a Desktop Alert"
I also like to turn off "Play a sound" and "change the mouse pointer"
I prefer to leave the 'Show an envelope icon in the taskbar" because that way, i can see some reminder to check my email"
Click "OK" to save your changes.
Now, you should no longer receive the desktop alert that shows your email.