You will need to be an administrator of your Office 365 account, with permission to grant consent for apps in order to revert Office 365 to Basic Authentication.
Warning: we recommend this is done by the person who administers and is familiar with your Microsoft Office 365 account.
Run diagnostic tool
Run the diagnosis tool and follow the guide to enable the Outlook Protocol: https://aka.ms/PillarEXOBasicAuth (this only allows the user to re-enable protocols that have already been disabled by Microsoft on their account).
The Protocol to Enable is “ Exchange Web Services.“
Once complete, move on to the steps below.
Step 1: Disable security defaults if enabled
1. Have the Admin follow this link:
Step 2: Re-enable basic authentication
1. In the Microsoft 365 admin center, go to Settings > Org Settings > Modern Authentication. In the Modern authentication flyout that appears, check box for Turn on modern authentication for Outlook 2013 for Windows and later (recommended). For allow access to basic authentication protocols check all boxes.