Exchange Server 2010 uses the concept of roles. A server with a particular role performs a specific functionality.There are five exchange 2010 server roles.
- Edge Transport server role
- Hub Transport server role
- Client Access server role
- Mailbox server role
- Unified Messaging server role
Edge Transport server role
The Edge Transport server role is a dedicated server function that performs spam and virus filtering as the first point of entry of messages into an Exchange Server environment and responsible for messaging routing purposes. The Edge Transport server role should never be a member of your internal domain, but should be a stand-alone server or member of an available perimeter Active Directory forest.
The various server roles can be combined onto a single server with the exception of the Edge Transport server role. For security reasons, the Edge Transport server role must be installed on a server.
Hub Transport server role
The Hub Transport role is a server role that is responsible for the distribution of mail messages within an Exchange Server organization,as well as applying transport rules, journaling policies, and delivery of messages to recipient mailboxes.Outbound mail is relayed from the Hub Transport server to the Edge Transport server and out to the Internet.There must be at least one Hub Transport role defined for each Active Directory site that contains a mailbox server, messages routes between Active Directory sites using an inherent connector called the intra-organization Send connector.
When you install the hub transport role on a server, the installation procedure creates two default receive connectors to allow the server to communicate with other Exchange servers within the organization and to accept messages from authenticated POP3 and IMAP4 clients.
Client Access server role
Microsoft introduced the Client Access Server role in Exchange 2007 to replace the previous situation where all mailbox clients either directly connected to the mailbox server or via a proxy.The Client Access Server role is responsible for serving client connections: Outlook, OWA,Outlook Anywhere, Exchange Active Sync, Exchange Web Services (EWS), and POP3 and IMAP4 protocols. Exchange Server 2010 uses Client Access servers to perform MAPI (the Messaging Application Programming Interface) on the Middle Tier (MoMT), all connectivity from mail clients is focused through these servers.
Mailbox server role
The Mailbox server role is the core role with in Exchange Server 2010 that stores the actual mailboxes of the user and mail enable objects such as contacts and distribution lists. Without mailbox servers to store the user data, all of the other server roles would be without purpose. The Mailbox server role also provides users with improved calendaring functionality, resource management, and Offline Address Book downloads. It is most likely only the Mailbox server role that can benefit significantly from using SAN or NAS technologies.
The public folder database is also on the Mailbox server role. Apart from public folders, the clients do not communicate directly with the Mailbox server but instead use the Client Access server for communication that then establishes the connection to the Mailbox server.
The Mailbox server role integrates with the directory in the Active Directory service much more effectively than previous versions of Exchange Server allowed, making deployment and day-to-day operational tasks much easier to complete.
Unified Messaging server role
Unified messaging is the capability for Exchange Server 2010 to be the voice mail server for an Organization, rather than having a separate voice mail system connected to the organization’s phone system. The Unified Messaging server role allows a user’s Inbox to be used for voice messaging and fax capabilities.
When implementing Unified Messaging with Exchange Server 2010, users can have access to voice, fax, and email messages all in the same mailbox, and these messages can be accessed through multiple client interfaces. The Unified Messaging server role also does not store any user-related information on the server but includes only configuration information such as custom auto-attendant files, grammar configuration, and Outlook Voice Access files.