Enable Modern Auth for pure On-Premises Exchange users

Summary 

Microsoft Exchange Server 2019 Cumulative Update 13 (CU13) introduces support in Exchange Server for OAuth 2.0 (also known as Modern authentication) for pure on-premises environments that use Active Directory Federated Services (AD FS) as a security token service (STS). 

To use this feature, you must be using Microsoft Outlook or any other client that supports Modern authentication by using AD FS. Currently, this feature is available only for Outlook on Windows. However, support for modern authentication will be added to other Outlook clients in the future.

For the prerequisites and steps to enable this feature, see Enabling Modern Auth in Exchange On-Premises.

Resolution

To add this feature, install Cumulative Update 13 or a later cumulative update for Exchange Server 2019.