When an incoming call was presented to users, they were accustomed to seeing a 9 or a 91 in front of a number in the phone CLID display. They liked this, as it allowed them to dial from the received calls or missed calls on their Cisco phones.
If a call went to voice mail, users were likely away from their phones and were picking up the messages on their smart phones remotely via an MS Exchange integration. The problem then was that the phone number couldn't be clicked and dialed from the smartphone with the same leading 9 or 91 used for outgoing calls on their desk phone.
- Incoming call from Joe's Pizza at 1(585)555-1212 shows up as 915855551212 on the Cisco phone display. This is good, as it can be returned from the phone's directories without editting the number.
- Incoming call from Joe's Pizza at 1(585)555-1212 gets forwarded to Unity Connection, and the message is delivered to your iPhone with the CLID of 915855551212. This is bad because the iPhone doesn't know you use a 9 in your office to make calls and considers it an invalid number.
My fix was to set the Calling Party Transformation Mask to XXXXXXXXXX on the voice mail's hunt pilot. This allows the 10 CLID digit format iPhone's like to be passed to Unity Connection. Then you also need to check Use Calling Party's External Phone Number Mask in the hunt pilot as well.