Use the appropriate link below for detailed instructions for your device.
It is up to the user if they want to use the Microsoft OUTLOOK App to send/receive email. The beauty of this app, is that you can switch from Mailbox to Calendar to Contacts and Tasks without leaving the app. In the Default mail app - it just knows MAIL, so you have to exit, and start Calendar, exit back to Mail...
The DEFAULT MAIL APP is the app that is previously downloaded on your device from the factory, while the OUTLOOK APP is downloaded by the user.