Setting up Office 365 email on Android Phone (using built-in gmail app)

Set up an Android device with a Microsoft® Office 365 or Exchange ActiveSync account

Gmail supports Microsoft® Office 365 and Exchange ActiveSync accounts, and comes pre-installed on all Android devices. To add your Microsoft® Office 365 or Exchange ActiveSync account to Gmail:

Open your device's Settings app. Tap Accounts. If you can't see 'Accounts', tap Users & accounts.
At the bottom, tap Add account.
Tap Exchange.
Enter your Microsoft® Office 365 or Exchange ActiveSync email and credentials.