SMS Notifications for Voicemail
Navigate to your domains control panel and enter the domain's user control panel.
Then navigate to the desired users' account.
Once in the users account page, navigate to "Change Account Security" and click the "+" symbol. In the field that appears enter desired SMS recipiant in the format phonenumber@messageserver as seen below.
Then navigate to the voicemail tab within the users account page
Within the voicemail panel select your your desired options within the "Unified Messaging" section.