Continuing my series on things that I did at Microsoft: in this part, I talk about outbound dialing rules that I implemented for Exchange Server 2007.
Exchange Unified Messaging server provides the functionality to place outbound calls. For eg, imagine a customer calling the corporate switchboard, and looking up the person he wants to talk to, using the AutoAttendant. Imagine that the target person is not in the US, and in order to call him, a long distance call will need to be placed.
It is possible that the company might want to prevent that call and instead route the caller to an operator. This is implemented by the concept of dialing rules.
The UM administrator can configure dialing rules on the AutoAttendant, DialPlan or Mailbox Policy. When the UM server needs to place an outbound call, it consults the dialing rules, and figures out whether the call is allowed. It also figures out the effective number to be called - this number will have the correct outside line access code (for eg: prepending the target number with a '9' to signify to the PBX that the numbe is an external number).
More details about this feature can be found in this article: http://msexchangeteam.com/archive/2007/01/29/432440.aspx which discusses how to create dialing rules.