The Unified Messaging Troubleshooting Tool is a diagnostics cmdlet which every administrator should run whenever someone desperately (or not) comes to them and says "Help! My voicemail isn't working!". The tool executes a set of tests and outputs the possible root causes for any detected issues and the possible solution for those. Simple, fast and efficient, just the kind of tool you need in your daily IT adventures.
As more and more organizations are starting to move away from the typical enterprise deployment model to a completely online world in Office 365, its right time you download and use this tool.