Multiple servers / want to share voicemail on one server

Can anyone help me setup the ability to share voicemail from one server to another? I program my devices with two different servers in case there are any outages, but want calls to ring on just one mailbox no matter what server the call originated from or terminated to.

Will gladly pay you for your time if you can show me how to set this up

Mark Cochenour
[email protected]