You can use the Message Forwarding Rule feature to send messages to any email address.
So you would need a mailbox class with MFR enabled, add an entry in the MFR settings of the mailbox., make sure you use WAV format. User will have to activate the rule by logging in to mailbox and pressing 8,5,1.
Or if you have MyCallPIlot they can log in that way and have more options like ability to change email address.