Kindly refer the below steps to configure an Office 365 email account on Outlook using exchange activesync mode.
Step 1: Go to Windows Control Panel > Mail and click Show Profiles.
Step 2: Click Add, enter a name for the profile, and confirm.
Step 3: Select Manual setup or additional server types, and click Next.
Step 4: Select Outlook.com or Exchange ActiveSync compatible service, and click Next.
Step 5: Type the below user, server, and login information then click on ‘Next’ button.
Username: Your Office 365 account
Password: Your Office 365 account password
Mail Server: outlook.office365.com
Step 6: When Outlook completes the test connection, click Close.
Step 7: Click Finish.