Note: OAUTH is not a supported way to see free/busy between two on-premises organizations.

First we check if we have OAUTH configured by looking for an Intra Organization Connector with the domain name of (assuming the Exchange server is 2013 or later).

The Availability Service on the Exchange server in Contoso then checks to see if there is a path for it to find the free/busy information for. The Exchange server in Contoso determines (usually based on target address of a mail-enabled user) that Ted is not local and has a domain name of set as the target address.ģ. Bill creates a meeting request and adds Ted as an attendee.Ģ. For this example, we will assume a user Bill (from Contoso) is looking up a user Ted’s (from Tailspin) free/busy information.ġ.

Now let’s look at how a cross organization availability requests works. The following is a diagram of the basic configuration between two organizations. In most scenarios, it is just a matter of configuring a Federation Trust and an Organization Relationship using the Exchange Admin Center (EAC). So, what does a typical configuration look like? However, before we get into why this could be a problem when you deploy a hybrid configuration, we need to make sure you have a general understanding of how the cross-organization free/busy works. The main point of this article is to understand what to do when one of these organizations deploys a hybrid configuration with Office 365. This set of features allows an organization to share limited free/busy details with another organization without an AD Trust in place.

It really started with the Availability Address Space feature in Exchange 2007, later moving on to the Microsoft Federation Gateway (Now called the Azure Authentication System) with Organization Relationships in Exchange 2010, 2013, and 2016.

This blog post discusses why free/busy is broken and what you can do about it.Ī bit of history of the Availability serviceįor many years now we have allowed different organizations to share calendar availability between each other. Suddenly, Contoso and Fabrikam users find availability information is not showing for the Tailspin mailboxes moved to Exchange Online. Then one fine day, one of the companies deploys a hybrid configuration and moves mailboxes to Office 365 in our example, it is Tailspin. For instance, you could have two or more companies on-premises sharing free/busy between each other. This scenario applies to companies with one or more external free busy relationships configured. During the recent Microsoft Ignite conference I heard questions related to hybrid and partner free/busy relationships quite often, so I wanted to write about it.

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