Applies to: Exchange Server 2007 SP3, Exchange Server 2007 SP2, Exchange Server 2007 SP1, Exchange Server 2007
Topic Last Modified: 2008-12-11

Incoming calls that are placed by users who are using the Play on Phone feature are received and routed by a computer that is running Microsoft Exchange Server 2007 that has the Unified Messaging server role installed. This topic discusses the message flow for calls that are made by a UM-enabled user who uses the Play on Phone feature in Exchange 2007 Unified Messaging.

Play on Phone

The Exchange 2007 Unified Messaging Play on Phone feature enables a UM-enabled user to access a voice mail message. However, instead of playing the media file over their computer speakers, they can listen to the message on a telephone.

When users sit in office cubicles, use a public computer, have a computer that is not enabled for multimedia, or have a voice message that is confidential, a UM-enabled user may not want to or may be unable to play a voice message over their computer speakers. The Play on Phone feature lets the UM-enabled user play the voice message over a telephone. The Play on Phone feature is available in Exchange 2007 Outlook Web Access and in Office Outlook 2007.

The Play on Phone feature only works with the primary mailbox in an Outlook profile. If you have Outlook configured to open more than one mailbox, you cannot use the Play on Phone feature to listen to voice messages from the additional mailboxes.

Figure 1 illustrates how Exchange 2007 Unified Messaging routes the incoming calls for UM-enabled users who use the Play on Phone feature.

Play On Phone Message Flow
The Unified Messaging Web services are installed on a computer that has the Client Access server role installed. Unified Messaging Web services enable Session Initiation Protocol (SIP) functionality on a Client Access server. This functionality enables a user to record a voice mail greeting or use the Play on Phone feature. The Unified Messaging server uses only SIP to communicate. Therefore, the UM Web service is installed on a computer running the Client Access server role and is required to enable the Client Access server to communicate with the Unified Messaging server.
By default, the Unified Messaging dial plan is not secured. This means that SIP data, including Unified Messaging Server settings and other call information that is sent between a Client Access server and a Unified Messaging server is unencrypted. This behavior could conflict with the security requirements at certain organizations. To help protect all SIP traffic, select a SIP Secured dial plan. This type of dial plan uses Transport Layer Security (TLS) to encrypt the SIP traffic between a Client Access server and a Unified Messaging server. The SIP Secured dial plan requires that the Unified Messaging server and the Client Access server both have certificates that are valid to each other in their corresponding FQDN names. For more information about SIP security and TLS, see Understanding Unified Messaging VoIP Security.

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Figure 1   Message flow for incoming calls when the Play on Phone feature is used