====== To PBX ======

  * This method is the default for DuVoice. 
    * DuVoice will send the SIP notify to the PBX directly.
    * Then the PBX will handle the MWI to the phones from that point.

===== Requirements =====

  * PBX must support forwarding the SIP notifies sent from DuVoice. 
  * Phone extension must match MWI field configured in DuVoice.
  * DuVoice must be licensed for SIP and integrated to a SIP PBX.

===== Mailbox =====

  * No special configuration must be performed in the mailbox.
    * Leave the MWI addresses as the extension, which is the default setting. 
      * Adding an IP address will cause notifications to fail.