You can partition voice mail ports into multiple voice mail hunt groups if desired (for example, to simulate multiple Auto Attendants by giving each hunt group different sets of greetings).
The main voice mail hunt group must contain all of the available ports, preferably in sequential order.
The main voice mail hunt group must also have the lowest DN of all other voice mail hunt groups used for alternate greetings.
Each voice mail hunt group must be of type VoiceMail.
A voice mail port can belong to the main voice mail hunt group, and one other voice mail hunt group.
For message waiting purposes, all call forwarding and call rerouting must be rerouted back to the main voice mail hunt group