UM Caller ID lookup from AD not working on internal extensions

Hi.  I’m setting up an Exchange 2010 SP1 UM box to show the use of Ex UM.  We’re configuring our internal help desk as a UM user (mainly so techies on call get transcribed messages with the VM instead of just an empty page to call the Unity server) and using this as our proof of concept to try and sway upper management to let us move from our old VM system to Exchange UM.

My problem is with the Caller ID lookup from the AD / GAL when calling from an internal four-digit extension.  When I call from an outside line (that is listed as my mobile number in AD) the full 10-digit caller ID number is passed and Exchange UM picks up that the call is from me, setting the From: address on the voicemail to my email and showing my info at the bottom of the message.

When I call from an internal number (1131, where my full number of 5555311131 is listed as my telephone in AD) the UM server doesn’t see it as me; the message subject is “Voce Mail from Russell”, the From: address is “Russell (No email address available)”, and the info at the bottom shows that Caller-Id is 1131.

If I UM enable my mailbox with extension 1131, then everything shows up properly.  So I know its searching for extensions in the same dialplan like it’s supposed to.  But my PoC relies on the UM server being able to caller-id match our internal extensions to our users’ accounts.

I have set AllowHeuristicADCallingLineIdResolution to $true and I have a NumberingPlanFormats of {531xxxx, 555531xxxx, 555535xxxx}  It is my understanding that this should allow the caller ID lookup to find 5555311131 by using 555531xxxx with the passed caller ID of 1131.  But this just isn’t working.

Any ideas on how to get the internal four-digit caller id to work with the AD / GAL lookup?  Or at least how to better diagnose the problem and see where this is breaking?

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Russell