This video presents a more detailed look at the five Server Roles in Exchange 2007.
The Mailbox Role as its name implies hosts the mailbox databases as well as any public folder databases, while also providing MAPI access to Outlook clients. The Mailbox Role is ordinarily installed with other roles on a single server, such as the Hub Transport Role, Client Access Server Role and the Unified Messaging Server Role.
The Client Access Server Role, on the other hand, is similar to the Front End Server in Exchange 2000 or 2003. The Client Access Server supports the use of Outlook Web Access for access using a web browser as well as Exchange ActiveSync for mobile devices. POP and IMAP are also implemented here, while Outlook Anywhere support allows Outlook clients to connect from outside the corporate network without the use of a VPN.
The Hub Transport Server Role will route messages within an Exchange organization and is similar to the Bridgehead Server found in Exchange 2000/2003. It can also be configured to route external email in lieu of the optional Edge Transport Server Role. The Hub Transport Server is reliant on the presence of Active Directory to have a logical infrastructure in place for the routing of internal messages.
The optional Edge Transport Server Role sits on the perimeter and is not part of Active Directory. In addition, an Exchange Server configured as an Edge Transport Server Role cannot also be configured as any other role. It main task is to sit on the perimeter of the network to provide security in the form of antivirus and anti-spam filtering agents and the implementation of organizational policies for an organization.
Finally, the Unified Messaging Server Role provides voice over IP capabilities to an Exchange Server in order to integrate e-mail, voicemail and incoming faxes as part of an inbox. Outlook voice access also opens the door to multiple access interfaces such as the phone. Given the potential complexity of telephony infrastructure such as IP-PBX and VoIP gateways, a telephony expert is suggested for the installation and configuration of the Unified Messaging Server Role.
Watch the video for a more detailed description of each role.