I haven't come across the code -1 with cisco appliances, but I've seen it elsewhere. Its something to the effect of server not reachable. It could also be an authentication issue. Did they do any exchange maintenance? Are they allowing unauthenticated mail on the exch server? Can you open a smtp connection w/ the server?
Configure Multicast Paging on the Cisco IP Phone 7800 Series or 8800 Series Multiplatform Phone
The Cisco IP Phone 7800 and 8800 Series Multiplatform Phones provide voice communication over an Internet Protocol (IP) network...
Add Call Park on a Cisco 7800 or 8800 Series Multiplatform Phone Key Expansion Module
Call park allows the user of the phone to put an incoming call on hold so that the call can be retrieved on another phone. A call is park...