Deep dive: How to configure Exchange on-premise Server hybrid integration with Office 365, test REST API calls?

This post has been republished via RSS; it originally appeared at: MSDN Blogs.

This is one of the regular discussion that comes across at my desk, how we can configure Hybrid Exchange on-premise server integration with Office 365/Exchange Online, so that users can make use of REST API. So I thought let me stitch all of them together which can be handy for both the Exchange administrators and REST API developers as well. This is a deep dive one stretching from administration, configuring, testing the API calls as well.

Exchange On-Prem 2016 Server CU3  + Office 365 + REST API integration:

Microsoft Graph has always provided access to customer mailboxes in the cloud on Exchange Online as part of Office 365. Exchange 2016 Cumulative Update 3 (CU3), released in September 2016 for Exchange on-premises servers, adds support for REST API integration with Office 365. If your app uses v1.0 of the Mail, Calendar, or Contacts API, you will now also find a seamless authentication and application experience in hybrid deployments, regardless of whether the mailbox is on-premises or in the cloud, provided that the deployment meets specific requirements.

Behind the scenes, when Microsoft Graph identifies that a REST API call is attempting to access an on-premises mailbox in a hybrid deployment, it proxies the REST request to an on-premises REST endpoint which then processes the request. This discovery makes accessing the REST API possible.

Requirements for the REST API to work in hybrid deployments

Le Cafe Cental de Deva - Deva blogs!!

Let’s do a detailed hands-on Exchange on-premise Server integration with Office 365/Exchange Online and play/the REST API calls:

Come learn how you can now use Microsoft Graph to reach on-premises and cloud users of hybrid Exchange 2016 deployments, in addition to Office 365 and  We'll discuss how your application can handle versions of servers on-premises and in the cloud, and how on-premises Exchange 2016 is set up to support Microsoft Graph and OAuth.

In addition, you can refer another related video (yes, definitely hands-on as well. It’s Level 300 training video, contains 75 minutes – but worth watching):

In this we will discuss how you set set up on-premises Exchange 2016 to support applications developed built on easy-to-use REST APIs, and how your application should handle versions of servers in cloud and on-premises.

Related resources for IT administrators:

Related resources for Graph API developers:

Le Cafe Central de Deva - Deva blogs

But you need to aware that (when you test the above hybrid scenario),

  • The ability to use these REST APIs in hybrid deployments is currently in preview.
  • Only v1.0 of the Mail, Calendar and Contacts API are available for mailboxes in hybrid deployments.
  • Other v1.0 API sets, such as the Groups API, or APIs in other versions, are not available.
  • If you attempt to use an API that is not part of the supported set in a hybrid deployment, you will get the following error message: "REST APIs for this mailbox are currently in preview. You can find more information about the preview REST APIs at"

Hope this helps.

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