Use REST APIs to access mailboxes in Exchange hybrid deployments (deprecated)
Microsoft Graph has always provided access to customer mailboxes in the cloud on Exchange Online as part of Microsoft 365. Exchange 2016 Cumulative Update 3 (CU3), released in September 2016 for Exchange on-premises servers, added support for REST API integration with Microsoft 365.
Effective July 2023, the ability to use these REST APIs in hybrid deployments is no longer available.
For more information, see The End of REST API Integration for Exchange on-premises - Preview.