Understanding Shared Free/Busy in Exchange 2003 Hybrid Deployments

Applies to: Exchange Server 2010 SP3, Exchange Server 2010 SP2

Sharing free/busy (calendar availability) information between users located on-premises and in the Microsoft Exchange Online organization is one of the primary benefits of a hybrid deployment. Users in both organizations can view each other's calendars just as if they were located in the same physical organization. This makes scheduling meetings and resources easy and efficient.

Several components in a hybrid deployment are required to enable the shared free/busy feature in a Microsoft Exchange Server 2003 deployment:

• Federation trust   Both the on-premises and Microsoft Office 365 service organizations need to have a federation trust established with the Microsoft Federation Gateway. A federation trust is a one-to-one relationship with the Microsoft Federation Gateway that defines parameters for your Exchange organization. The gateway uses these parameters when acting as a trust broker between your on-premises and Office 365 service organization to exchange free/busy information between on-premises and Exchange Online organization users.

  By default, a federation trust with the gateway is automatically configured for your Office 365 service organization when the account is created. The Manage Hybrid Configuration wizard automatically checks to see if there is an existing federation trust with the Microsoft Federation Gateway for the on-premises organization. If present, the existing federation trust is used to support the hybrid deployment. If not present, the wizard creates a federation trust for the on-premises organization with the Microsoft Federation Gateway. The wizard also adds any domains selected within the Manage Hybrid Configuration wizard to the on-premises organization federation trust.

  Learn more at: Understanding Federated Delegation

• Organization relationships   Organization relationships are needed for both the on-premises and Exchange Online organization and are configured automatically by the Manage Hybrid Configuration wizard. An organization relationship defines the level of free/busy information shared for an organization.

  By default, the free/busy data access sharing level is Free/busy access with time, plus subject and location for both the on-premises and Exchange Online organization relationships. If you want to modify the free/busy sharing access between your on-premises and Exchange Online organization users, you can manually configure the organization relationship access level after the Manage Hybrid Configuration wizard has completed.

  Learn more at: Understanding Federated Delegation

• Hybrid Mailbox server   Exchange 2003 organizations must have a hybrid server with the Service Pack 3 (SP3) for Exchange 2010 Mailbox server role installed to support free/busy sharing between on-premises and Exchange Online mailboxes. Free/busy information for Exchange 2003 mailboxes is stored in public folders and the free/busy information in your existing public folders must be replicated to the hybrid Mailbox servers. Client requests for free/busy information are automatically directed to the hybrid Mailbox servers for processing for both on-premises and Exchange Online organization users after the hybrid deployment is configured by the Manage Hybrid Configuration wizard. To avoid a single point of failure for these public folder replicas, you should consider adding more than one hybrid Mailbox server to your on-premises organization for redundancy.

When configuring your organization for a hybrid deployment, configuring shared free/busy calendar access is automatically configured by the Manage Hybrid Configuration wizard in all scenarios. Creating a federation trust with the Microsoft Federation Gateway and configuring organization relationships for the on-premises and Exchange Online organization are hybrid deployment requirements. If you don't want to allow free/busy sharing between your on-premises and Exchange Online organization users in the hybrid deployment, you can manually disable free/busy sharing by using the Shell and the Set-HybridConfiguration cmdlet after the Manage Hybrid Configuration wizard has completed.

The hybrid deployment features shown in the following table have a dependency on federation trusts and organization relationships.

Hybrid deployment free/busy information is supported in the following clients:

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