Exchange 2010 Server Roles (part 3) - Unified Messaging Server, Edge Transport Server

2.4. Unified Messaging Server

The Unified Messaging server role was introduced in Exchange Server 2007 and is reasonably similar in Exchange Server 2010. There are a few useful new features such as voicemail preview, protected voicemail, and the personal auto-attendant. One notable change is that the inbound faxing function is no longer supported. This server role integrates voicemail with Exchange mailboxes and provides voice auto-attendant functions and phone access to email and calendar. The Unified Messaging server requires an IP-based telephone switch or a traditional public branch exchange (PBX)-to-IP gateway.

The Unified Messaging server role integrates into your environment, as shown in Figure 6. This server must be in the same Active Directory site as a Hub Transport server and preferably the same site as the Mailbox servers that hold the mailboxes it is supporting. Further, the Unified Messaging server roles should sit on the same subnet as the IP-based PBX or PBX-to-IP gateway.

Figure 6. Integrating a Unified Messaging server role

The following functions are handled by the Unified Messaging server role:

• Accepts inbound VOIP phone calls for users if they do not answer their voice line in the same way that a traditional voicemail system accepts calls. The VOIP system or PBX-to-IP gateway passes along identifying information to Unified Messaging, indicating which phone extension had been called.

• Identifies which user mailbox a phone call is intended for and retrieves the user's outgoing message from their mailbox.

• Provides voicemail for users of the IP-based phone system or through the PBX-to-IP gateway; includes voicemail greetings and options. Inbound voicemail is recorded as a Windows Media Audio (WMA) file and stored as a message in a user's Inbox.

• Allows users to dial into the Unified Messaging server to retrieve voicemail, listen to email messages, review their calendar, or change appointments

• Provides voice menus and prompting call menus acting as an auto-attendant system.

If you look in the service console on a server with the Unified Messaging role installed, you will see the services shown in Table 4.

2.5. Edge Transport Server

The Edge Transport functionality is another new feature that was included with Exchange Server 2007. The Edge Transport server provides a slimmed-down version of the Exchange message transport functionality that requires neither Active Directory nor components such as the information store.

The Edge Transport server is usually placed in an organization's perimeter network rather than the internal network, as shown in Figure 7.

Figure 7. Implementing an Edge Transport server role

There are a number of reasons that the Edge Transport role has advantages over using an Exchange 2003 server in your perimeter network:

• To process delivery reports, nondelivery reports, and address rewrites, the information store service must be running and the default mailbox database must be mounted.

• Placing an Exchange 2000/2003 server in the perimeter network requires many ports to be opened on the firewall from the perimeter network to the internal network.

• Allowing inbound email directly to an Exchange server could jeopardize both Exchange and Active Directory.

For these reasons, a server role was developed that has many of the advantages of an Exchange 2010 server. However, it can be made much more secure because it can run in the perimeter network as a stand-alone computer and does not require Active Directory membership. Here are some of the characteristics of the Edge Transport server role:

• It should be deployed in the perimeter network.

• It can be managed with Exchange Management Shell scripts and the Exchange Management Console in much the same way a regular Exchange server is managed.

• The Edge Transport server receives LDAP updates from an internal Hub Transport that updates information such as valid SMTP domains, recipients, and safe sender and blocked sender lists for each user.

• The only components required to run the Edge Transport role are the message transport system and an instance of the Active Directory Lightweight Directory Services database.

• Features such as transport rules can be implemented in the perimeter network and provide message policy enforcement for messages entering or leaving the organization that is separate from that provided on the internal network.

• Connectivity between internal Hub Transport servers and Edge Transport servers is authenticated and the data stream encrypted.

• The content filter functionality and other antispam and message security tools are built in, as is the ability to add third-party content filtering/message hygiene tools.

• Microsoft Forefront Security for Exchange Server can be employed on the Edge Transport server role for virus detection and quarantine.

For medium and large organizations, higher availability comes in the form of installing multiple Edge Transport servers and providing load balancing using multiple DNS Mail Exchanger (MX) records, network load balancing, DNS round-robin, or failover using multiple Internet connections.

If you look at the service console on an Exchange Server 2010 Edge Transport server, you will find the services in Table 5.