Recently I’ve bumped into a strange issue, when setting up an Exchange Hybrid Scenario on a customer. The customer has a pure Exchange 2013 on premises, with no legacy versions of Exchange, and when you run the Exchange Hybrid configuration wizard it will try and configure OAuth authentication between the Exchange On Premises and Exchange Online. The problem I had was, when trying to configure the OAuth authentication I was getting the following error:
“Exchange OAuth authentication couldn’t find any accepted domains in your on premises organization. Verify that you’ve configured at least one on-premises accepted domain.”.
So what was the actual real impact of the error above? The answer is: Free/busy information between Exchange online users and Exchange on-premises users, on both directions, was not working? Why? Well i am going to try and keep the explanation simple and focus more on the solution. Free/busy was broken because it relies on IntraOrganizationConnectors, and the IntraOrganizationConnectors rely on OAuth authentication.
The first thing that i did was to check if my accepted domains on-premises were ok. I ran on the on-premises Exchange Management Shell:
the output showed all my on premises domains, as expected, and the *.onmicrosoft.com domains created by the Hybrid Wizard. So all good here.
The next step was to check the IntraorganizationConnectors. I ran both on the on-premises and online Exchange Management Shell:
The main purpose here was to make sure that the IntraOrganizationConnector was there and enabled. I verified that i had both connectors, one on-premises and one online. Then i disabled the connector to force the Free/Busy information to be handled by the OrganizationRelationship. I ran on both Exchange Shells:
Set-IntraOrganizationConnector <Connector Name> -Enabled $false
You need to wait up to one hour to test the Free/busy from an online to an on-premises user. From one on-premises to one online should be almost instant, depending of course on Active Directory replication.
So did disabling the IntraOrganizationConnectors fixed the Free/Busy issue? For me it did, which means that i had the issue identified.
When i ran the Hybrid Configuration Wizard, the OAuth authentication was only partially configured, and therefore the IntraorgConnectors were not working. Disabling them or removing them sorted the issue, but that is not the ideal solution, as the goal is to use them correctly.
And what was the solution? To manually configure the OAuth authentication between my Exchange on-premises and Exchange Online. To do that follow all the steps from the link below, and you should get your problem sorted, as i got mine. Any questions or comments let me know.
I hope that the post above was helpful!