With Exchange Server Setup, you can deploy servers with specific roles through¬out the enterprise. Prior to setup and configuration, you need to decide how you will use Exchange Server 2010, what roles you will deploy, and where you will locate those roles. Afterward, you can plan for your deployment and then roll out Exchange Server.
Exchange Server 2010 implementations have three layers in their architecture: a network layer, a directory layer, and a messaging layer. The messaging layer is where you define and deploy the Exchange Server roles. The Exchange servers at the core of the messaging layer can operate in the following roles: Mailbox Server
This is a back-end server that hosts mailboxes, public folders, and related messaging data, such as address lists, resource scheduling, and meeting items. For high availability of mailbox databases, you can use database availability groups.
Client Access Server
This is a middle-tier server that accepts connections to Exchange Server from a variety of clients. This server hosts the protocols used by all clients when checking messages. On the local network, Outlook MAPI clients are connected directly to the Client Access server to check mail. Remote users can check their mail over the Internet by using Outlook Anywhere, Outlook Web App, Exchange ActiveSync, POP3, or IMAP4.
Unified Messaging Server
This is a middle-tier server that integrates a private branch exchange (PBX) system with Exchange Server 2010, allowing voice messages and faxes to be stored with e-mail in a user’s mailbox. Unified messaging supports call answering with automated greetings and message recording, fax receiving, and dial-in access. With dial-in access, users can use Outlook Voice Access to check voice mail, e-mail, and calendar informa¬tion; to review or dial contacts; and to configure preferences and personal options. Note that to receive faxes, you need an integrated solution from a Microsoft partner.
Hub Transport Server
This is a mail routing server that handles mail flow, rout¬ing, and delivery within the Exchange organization. This server processes all mail that is sent inside the organization before it is delivered to a mailbox in the organization or routed to users outside the organization. Processing ensures that senders and recipients are resolved and filtered as appropriate, content is filtered and has its format converted if necessary, and attachments are screened. To meet any regulatory or organizational compliance require¬ments, the Hub Transport server can also record, or journal, messages and add disclaimers to them.
Edge Transport Server
This serves as an additional mail routing server that routes mail into and out of the Exchange organization. This server is designed to be deployed in an organization’s perimeter network and is used to establish a secure boundary between the organization and the Internet. This server ac¬cepts mail coming into the organization from the Internet and from trusted servers in external organizations, processes the mail to protect against some types of spam messages and viruses, and routes all accepted messages to a Hub Transport server inside the organization.
These five roles are the building blocks of an Exchange organization. Note that you can combine all of the roles except for the Edge Transport server role on a single server. One of the most basic Exchange organizations you can create is one that includes a single Exchange server that provides the Mailbox server, Client Access server, and Hub Transport server roles. These three roles are the minimum required for routing and delivering messages to both local and remote messaging clients. For added security, you could deploy the Edge Transport server role in a perimeter network on one or more separate servers.