What is the role of the "Client Access Server" in an Exchange deployment?

The Client Access Server (CAS) plays a critical role in managing the connections from clients to the Exchange Server environment. It provides the necessary services that allow various client applications, such as Outlook Web App (OWA), mobile email clients using ActiveSync, and other email clients, to connect to mailboxes hosted on the Exchange servers.

By centralizing client access, the CAS allows for a more streamlined and manageable system where it acts as a gateway for users seeking to access their email, calendars, and other mailbox features. It does not perform tasks related to email routing, archiving, or backups, which are dedicated functions of other server roles. This specialization allows the CAS to efficiently handle incoming requests and deliver the required resources without being tied to the backend processes such as routing or data storage.

Understanding the specific functions of the Client Access Server helps in appreciating its importance in ensuring user connectivity and experience within an Exchange deployment.