OAuth Authentication in the Synchronizer

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Currently, we have two ways of authenticating users with the Exchange Online Synchronizer. We support Basic Authentication and OAuth.

Basic Authentication

This is basically the way the Synchronizer has been running for many years. Meaning, there is a dedicated domain user, the SyncUser, who is given Impersonation or Delegation rights.

Basic Authentication is still applicable for Exchange OnPremise environments.
For all the preparation and installation articles, please see the sections Prepare and Install


Microsoft has decommissioned Basic Authentication for EWS. This applies only to the cloud-based Microsoft 365/Exchange Online products; there are no changes to EWS capabilities of on-premise Exchange products , more info


The Synchronizer uses EWS (Exchange Web Services) and supports the latest OAuth authentication and authorization techniques.

Let's explain:

  • For On-Premise Exchange customers nothing will change, you can still use the Synchronizer the way you are used to. Install the latest version to get the latest features and fixes.
  • For M365/Exchange Online customers, OAuth will need to be used. If you need to relink the syncusers with the Microsoft 365 Token Authentication Manager, see this article
  • For M365/Exchange Online customers who use the Synchronizer in ranked mode, OAuth needs to be used. This means that the linked users will need to be re-linked with the Microsoft 365 Token Authentication Manager. See this article
  • For Exchange On Premise customers migrating to M365/Exchange Online who have to start using the Synchronizer with OAuth, but do not want to move all users in 1 go, the Synchronizer can be used in a mixed mode. Using the Sync in mixed mode, both in Basic Authentication and OAuth, gives you the change to move the users in smaller parts. More information

OAuth and the Microsoft 365 Token Authentication Manager

In the Synchronizer we use the Microsoft 365 Token Authentication Manager to let the users themselves authorize the Synchronizer to their Calendar.

How the Microsoft 365 Token Authentication Manager works is described in this article.

If your environment is eligible, it is possible to migrate to Synchronizer for SuperOffice (Cloud Synchronizer). Please use our online chatbot to find out which synchronizer fits you best.