In September of 2019 Microsoft announced that they would retire Basic Authentication for services that access Exchange Online from October 13th 2020.

Microsoft announced on 3rd April 2020 that the retirement date for Basic Authentication for Exchange Online would be deferred until the second half of 2021.
https://developer.microsoft.com/en-us/office/blogs/deferred-end-of-support-date-for-basic-authentication-in-exchange-online/

The services within Exchange Online that Sage CRM features may access are

• Exchange Web Services (EWS)
• Post Office Protocol (POP)

Note: This does not impact on-premise implementations of Microsoft Exchange which can still use Basic Authentication.
Note: This change does not impact SMTP AUTH.

Sage will implement OAuth 2 (Modern Authentication) in Sage CRM 2020 R2 to enable the Exchange Integration to connect to Exchange 365/Exchange Online.