Office 365 business subscription.
Android version 6.0.1.
I'm using the official outlook app for android, most recently updated from the app store as at 0700GMT 27 june.
I tried performing a reset using the application on my account (the button reset under the account's details in the settings part of the app). No email came through. This also lost the calendar and everything else, which wouldn't sync properly. The
reset had the helpful tip "try resetting your account to deal with sync issues".
I then flushed the application's data and logged back into my account, which instantly downloaded and showed me all my email.
This happens regularly to my app, on the order of once every 2 to 3 weeks.