Forum Discussion
Microsoft Graph API support for on premise Exchange
I think it is possible now (Public Preview) but you need to have a Hybrid Exchange scenario.
https://docs.microsoft.com/en-us/graph/hybrid-rest-support
In specific, check out the following statement in the subsequent link of the shared link:
"But we have no plans currently to change the way EWS works on-premises, so using Graph for Exchange Online and EWS for Exchange Server on-premises is the current recommendation."
(this comes with the hint that you can also https://learn.microsoft.com/en-us/exchange/client-developer/exchange-web-services/how-to-authenticate-an-ews-application-by-using-oauth for accessing Exchange Online only, if the Graph API switch does not work for you)
EWS online will be retired with Oct 2026, so the golden rule today (Oct 2023) is:
1. use EWS for on-premise Exchange
2. use Microsoft Graph for Exchange Online
And since MS also retired the EWS Client Libs https://github.com/OfficeDev/ews-java-api / https://github.com/OfficeDev/ews-managed-api you are forced to create your own clients for the on-prem EWS API.
