Before you begin, update the Gmail app to the latest version:
Open the Google Play Store app on your phone or tablet. Type “Gmail” into the search bar and then select Update. Note: If the update option is not available, you’re already on the latest version.
Open the Gmail app.
Tap the menu icon in the upper left corner > Settings > Add account > Exchange and Microsoft 365.
Important: Do NOT choose “Outlook, Hotmail, and Live” unless you want to sync email only and not calendar/contacts.
Enter your full email address and tap Next.
Enter your password and tap Next.
Follow steps for your account type:
Microsoft 365 work: you may see a Redirect request screen. Tap OK.
If you see a Redirect request, tap OK.
On the Incoming server settings screen, change your server to outlook.office365.com.
Follow any prompts you may get for security or device permissions, sync settings, and more.
Click OK on any prompts you may receive.
You have a Microsoft 365 work or school account, so you may also be asked to confirm Remote security administration and approve additional security measures. In this case, choose OK or Activate.
Go to the inbox you just set up. If you see an email that says “Action Required to Sync Email,” open it and tap Use another Mail app instead.
If you don’t see this message and emails are syncing, skip this step.
Pull down the Android notification bar by swiping down from the top of your screen.
If you see a notification that reads “Unable to sync calendar and contacts,” tap it. Then tap Allow to give access and you’re done!
Note: If you don’t see a sync error, verify your calendar and contacts are syncing.
Enter email address. Tap Continue. When asked to select an email provider, choose IMAP.
If you want to use POP to access your email in Outlook.com, you’ll first need to enable POP access.
Select Settings 
> View all Outlook settings > Mail > Sync email.
Under POP and IMAP, select Yes under Let devices and apps use POP.
Select Save.