Step 1: Sign into Office 365 admin portal via https://portal.office.com
Step 2: Click on Admin from the left pane and navigate to Users >> Active users.
Step 3: On the Active users page, click on the Multi-factor authentication button on the top.
Step 4: Select the user from the list of users and click Manage user settings.
Step 5: Check all the three check boxes and click Save.
Step 6: Now sign into the user account via https://outlook.office365.com/
Step 7: In the More information required prompt click Next.
Step 8: In the next page, select country and enter the contact number to receive OTP and click Next.
Step 9: In the next page, enter the code and click Next and copy the App Password from the next page and click Done.
Step 10: Now, open the Outlook client and enter the app password while it prompts for the password.