Hello - I just had this problem come up a day or so ago. A small group of users started getting voicemail delivered to their external email addresses (they are not on our domain, but in our building and use our phones). The messages don't show up in their voicemail, and mwi doesn't come on. I'm trying to figure out what could be causing this. It doesn't appear that any changes were made to their exchange accounts or voicemail accounts.