The fact that the FCOS is being changed back to one labeled "GUEST" intrigues me. Is this a hospitality setup where there's a PMS (property management system) interfacing with the NuPoint? If so, sounds like that mailbox was somehow associated with a guest room, and when the room is checked out in PMS, that message is then sent to NuPoint which is set to reset the mailbox back to pre-defined settings.