1. Go to your iPhone or iPad's Settings > scroll down and tap Accounts & Passwords > Add Account.
Note: If you're on iOS 10 or later, go to Mail > Accounts >Add Account.
2. Select Exchange.
3. Enter your Microsoft 365 email address and a description of your account. Tap Next.
4. Tap Sign In.
5. Enter the password associated with your email account. If asked Work or Personal Account Click WORK, Tap Sign in or Next.
6. The Mail app may request certain permissions. Tap Accept.
7. Choose the services you want to sync with your iOS device and tap Save. You're done!
8. If you can't see all of your mail, your sync setting by default might not be including everything to save data, to change this go to your iPhone or iPad's Settings > scroll down and tap Accounts & Passwords > Add Account.
Note: If you're on iOS 10 or later, go to Mail > Accounts
9. Select Mail Days to Sync:
10. Select No Limit if you wish to Sync Everything, otherwise set to to something smaller to save data on the run: