Azure Access Control Service (ACS) has been deprecated by Microsoft Azure team. Any existing Dynamics 365 service bus that has been configured with ACS authentication will be impacted when ACS goes out of support.
With the deprecation of ACS, and the ability to configure ACS based authentication for Dynamics 365 Service bus has become progressively more difficult via PowerShell, Dynamics 365 products team took a direction change in how service bus registration worked to be 100% compliant with the current feature set of Azure.
The service endpoints created on Microsoft Dynamics CRM Version 8.1 (Microsoft Dynamics CRM Online 2016 Update 1) and Dynamics CRM Version 8.2 (December 2016 Update for Microsoft Dynamics 365) with ACS Authentication are the impacted versions. Any orgs updated from older versions of Dynamics CRM will continue to function on ACS, however the first update to the Service Bus registration will require it to be changed to a SAS key.
To identify whether your Dynamics 365 has Service endpoints that are authenticating using ACS, login to Dynamics 365 as an administrative user. Click Settings > Customization > Customize the System. Click Service Endpoints to see the list of registered endpoints.
There are two possible scenarios that you have configured Service Bus endpoint using ACS:
If you have already deprovisioned Microsoft Dynamics Marketing, it is still recommended to unregister the service endpoint using the Plugin-registration Tool
– Ramana Sridhar Vaidyanathan