Android Gmail

First, you may need to remove your POP/IMAP account.

Open Gmail.

In the upper-right corner, tap your profile and Manage accounts on this device.

Tap your POP/IMAP email account.

Tap Remove account > Remove account

Next, add your new Exchange account:

Tap your profile > Add another account

Tap Exchange and Office 365.

Follow the prompts to enter your email address and password.

(You might need to choose your account type as Work or School.)

If asked, tap Accept to allow Gmail to access your account.

When your account is ready, tap Done.

Nice work! You've updated your email to Exchange settings on this device.