The Mailbox server role, similar to the Client Access Server (CAS) role, has undergone some great changes in Exchange 2013. While in Exchange 2010 this role basically provided for message storage, in 2013 it also includes components previously found in separate roles such as Transport service, Client Access protocols, and Unified Messaging components. Mailbox servers now host every component and protocol that renders, processes, and stores user data.

As mentioned in Chapter 1, Getting Started, Exchange 2013 is made up of two foundational blocks: Client Access array and Database Availability Group (DAG), each providing an element of fault tolerance and high availability, decoupled from each other.

In this chapter, we will explore how to achieve high availability with the Mailbox server in Exchange 2013. Although the way this is achieved is still through the deployment of one or more DAGs, this technology has slightly improved compared to...