Microsoft postpones disabling Basic Authentication in Exchange Online for those still actively using it until the second half of 2021. Starting October 2020, Microsoft will still automatically disable Basic Authentication for all newly created tenants and on those where it is not actively used. Basic Authentication (also known as proxy authentication or legacy authentication) is the process through which desktop and mobile apps are sending username/password pairs on every request made when connecting to servers, endpoints, or online services, with the users’ credentials often being stored locally on their device.
Source: https://www.bleepingcomputer.com/news/security/microsoft-and-google-postpone-insecure-authentication-removal/