Once you setup your Office 365 Outlook account on your phone. It is highly suggested to TURN OFF the Focused Inbox setting that reduces the emails it shows you in the app. To do this:

1. Click on the round icon at the top left of the MAIL screen in the Outlook app

2. Click on the GEAR icon at the bottom left of the screen

3. Scroll down until you see the FOCUSED INBOX option

4. Click on the blue slider button until it turns gray

Now the Outlook app will show you all the email tha is sent to your account instead of deciding for you which email you should be seeing.