The Exchange 2010 hybrid server enables communication between your existing Exchange 2003 servers and the cloud-based service. The hybrid server consists of the Client Access, Hub Transport, and Mailbox server roles.

1. Download Exchange 2010 Service Pack 1 (SP1).
2. To obtain a Hybrid Edition product key, contact Office 365 support.
3. Install Exchange 2010 Server
4. Provide an Exchange 2010 Hybrid Edition product key on the hybrid server when you configure a hybrid deployment with Office 365.