Field Notes: Meeting the requirements for Interoperability between Microsoft Teams and Microsoft Exchange Server

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In this blog post, I want to walk you through my experiences with setting up and enable the interoperability between Microsoft Teams and on-premises Microsoft Exchange Server environments.

Since the beginning of this year, Microsoft Teams adoption has seen a tremendous uptick in usage. Organizations needed to adopt Microsoft Teams as their Unified Communications (UC) platform, but the other cloud migrations went on the back burner or were not even in scope anymore for this year. All is fine, until somebody asks: "I don’t see my calendar in Microsoft Teams… Can you fix this?"

Sure we can. In this blog post, I'll walk you through the process of enabling the interoperability between the Microsoft Teams service and the on-premises Microsoft Exchange Server environment.


Let's start with listing the Microsoft requirements and what they actually mean in real life:

Known requirements

We start with the known requirements as listed here. Summarized these are:

  • The employee identities need to be synchronized to Azure AD;
  • The organization needs to have the Exchange Hybrid option in Azure AD Connect;
  • OAuth authentication between your on-premises Exchange and Exchange Online organizations needs to be configured;
  • Microsoft Teams scheduling of meetings by delegates require an additional partner application;
  • The employees need to have to be licensed: the Microsoft Teams license to be specific;
  • The on-premises Microsoft Exchange Server environment needs to run Microsoft Exchange Server 2016 CU3 or a newer version of Microsoft Exchange Server.
  • Good to know: The Microsoft hybrid Agent (Modern Exchange Hybrid) cannot be used for the Microsoft Teams calendar integration. It is listed here in the constraints of the Microsoft Hybrid Agent.

My approach

When a customer asks “I want to have my calendar visible is Microsoft Teams, is this possible for us and what do we need to do?”, then this is my approach:

To see if it’s even possible to realize the interoperability, we need to validate the current on-premises Microsoft Exchange Server environment in terms of the version: It needs to run at least Microsoft Exchange Server 2016 with CU3. The importance of this question is in the availability of the new AutodiscoverV2 and the new REST-based application programming interface (API) in the Exchange Web Services (EWS) capabilities. But that is not all: In order to benefit from these new capabilities, the mailbox needs to be homed on a Exchange Server 2016 CU3 or higher mailbox server. If this is all true, then I validate if Autodiscover service and Exchange Web Services of Exchange Server 2016 is accessible from the internet. If not, the organizations must be willing to allow this.

Initial checks

This results in the following checks:

  • Autodiscover and Exchange Web Services (EWS) need to be accessible from the internet and pointing to a Microsoft Exchange Server that runs at least Microsoft Exchange Server 2016 CU3;
  • The mailboxes for the employees in scope need to be homed on a Microsoft Exchange Server hat runs at least Microsoft Exchange Server 2016 CU3;
  • The employees must have Microsoft Teams licenses assigned;
  • Good to Know: Microsoft Teams will not use the configured hybrid configuration within Exchange Online, but trusts the native Autodiscover functionality. Via autodiscover.domain.tld it is pointed to the on-premises environment or via SRV records it needs to point to the on-premises environment.
  • Good to Know: Autodiscover (http) redirect will not work for the Microsoft Teams integration. This might impact the current public certificates that an organization might currently use.

If any of requirements are not met or not possible to achieve, then the integration is a NO GO.

Further implementation information

When the initial requirements are all met, we can ask the following questions:

  1. Are there any Microsoft Exchange Server left in the organization that run Microsoft Exchange Server 2010?
    If a Microsoft Exchange Server 2010 is present in the environment, then the Exchange Hybrid configuration wizard will not create the OAuth configuration with Azure AD during the setup and we need to do it manually.
  2. Is a Exchange Hybrid configuration desired and on the roadmap for the organization?
    Exchange Hybrid is a requirement from Microsoft for the interoperability between Microsoft Exchange Server and Microsoft Teams. If we cannot use the Exchange Hybrid configuration wizard (which is the preferred option),  we need to configure the Oauth configuration manually
  3. Is it required that delegates need to be able to make appointments on behalf of the delegator?
    If so, we need to perform steps 2 and 3 of the instructions listed here. The steps will provision the trust for the Skype for Business online integration.
  4. Can we configured the Exchange Hybrid Writeback permission on the AD Connector account in Active Directory for Azure AD Connect?
    Within Azure AD Connect we need to enable the synchronization option for the Exchange Hybrid feature. This requires that the configured service account has the correct writeback permissions for Exchange attributes. The list of required attributes to which we need write permissions is listed here.


Compared to what is documented in the Microsoft docs and the real world, some parts are missing in the explanation or the requirements list of Microsoft. In this blog post I want to give you my past experience and help you with the little details to enable organizations to implement the calendar integration.

2 thoughts on “Field Notes: Meeting the requirements for Interoperability between Microsoft Teams and Microsoft Exchange Server”

    1. Hi RKast,

      Thank you for your feedback.
      I have updated the post with this information.

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