You are designing a Cisco Unity voice-mail-only solution to allow all outside callers at any of the 14 different company offices to locate any of the 7500 users by simply spelling the name of the user via the touch-tone telephone keypad in an Automated Attendant conversation. Each office has a different voice-mail system that you will replace with the new Cisco Unity solution. Each office also has a separate telephone system. The telephone systems come from various manufacturers. Users dial individual 10-digit phone numbers to reach each user. There is no telephone networking between offices. Many of the telephone systems will not allow conferencing and have a limited number of trunks for each office. The customer is not willing to change the telephone system structure at this time.

Which solution best meets the customer needs?

A.
This can be done with VPIM, which is an industry standard that allows different telephone systems to integrate over the Internet.

B.
This can be done with the optional Cisco Unity PBX conference feature that allows transfers between different PBXs by using the Intel Dialogic voice cards installed in all Cisco Unity servers.

C.
You can network the Cisco Unity systems together for subscriber-to-subscriber messaging, but to fulfill the requirements they want for Automated Attendant transfers between offices, they need to change to a networked telephone system solution.

D.
Create a new forest/domain and add one Cisco Unity server at each office. All Cisco Unity systems are member servers in the forest/domain and are provisioned for the number of users at that site. On one Cisco Unity server a dialing domain is created and all other Cisco Unity servers join that dialing domain. The directory handler search scope is set to that dialing domain.