Applies to: Exchange Server 2007 SP3, Exchange Server 2007 SP2, Exchange Server 2007 SP1, Exchange Server 2007
Topic Last Modified: 2006-05-10

This section introduces topics that describe how Microsoft Exchange Server 2007 Unified Messaging handles message flow in different incoming call scenarios.

Incoming Calls Overview

Exchange 2007 Unified Messaging handles the following types of incoming calls:

  • Voice

  • Fax

  • Outlook Voice Access

  • Play on Phone

  • Auto attendant

Call handling is a term that describes how incoming calls are answered and handled by a computer that is running Exchange 2007 that has the Unified Messaging server role installed.

When an incoming call is received by an Exchange 2007 Unified Messaging server, the call is answered and then routed by using a message transport such as Simple Mail Transfer Protocol (SMTP), MAPI, remote procedure call (RPC), or Lightweight Directory Access Protocol (LDAP). The message transport that is used when messages are routed depends on the type of incoming call that the Unified Messaging server answers.

Exchange 2007 Unified Messaging depends on the Active Directory directory service to route incoming calls. Each UM-enabled recipient must have a telephone extension number listed in Active Directory for call answering to function correctly. The extension number for the recipient is listed in Active Directory and is mapped to the extension number that is configured on the user's UM-enabled Exchange mailbox. When a Unified Messaging server answers a call, an Active Directory lookup is performed to locate the appropriate UM-enabled recipient and the message is routed to the recipient's mailbox.

Message Flow

Message flow in Unified Messaging is the process by which a message that is received by a Unified Messaging server is routed in an Exchange 2007 organization. Depending on the type of incoming message or call that is answered by a Unified Messaging server, a different transport protocol is used.

In earlier versions of Exchange, routing groups were used to route messages between bridgehead servers—known in Exchange 2007 as Hub Transport servers. There are no routing groups in Exchange 2007.

For example, in an incoming call scenario that includes incoming voice and fax messages, a Hub Transport server uses the SMTP transport to submit the voice or fax mail message to the Mailbox server. In a routing scenario that includes multiple Hub Transport servers, the incoming voice or fax mail message is first submitted to the closest Hub Transport server and is then routed to the appropriate Mailbox server that contains the UM-enabled mailbox.

To make sure that all incoming messages are transmitted and delivered to UM-enabled recipients, the Unified Messaging servers use a spooling or re-try algorithm. The Unified Messaging servers try to connect to a Hub Transport server every 30 seconds to submit all messages that are stored on the Unified Messaging server.

For more information about how the Exchange 2007 Unified Messaging server handles incoming calls and how the messages flow in Exchange 2007 Unified Messaging, see the following topics:

For More Information