Turning Off Outlook's New Mail Alerts

To turn off Outlook's popup alerts telling you that new mail has arrived, take the following steps in Outlook:

1. Click on File.
2. Click on Options.
3. Click on Mail.
4. Under Message arrival, clear the checkbox for Display a Desktop Alert.

Applies to Outlook 2010 to 2013

References:

1. Turn on or off new message alert pop-up window
   Office.com

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