If VLC doesn't have a preview handler for Outlook, or if you are unable to listen to voicemails through Outlook, there could be a problem with file association inside Windows. By default, all .wav files should be associated with VLC Media Player, and incorrect configuration can cause these problems. You can resolve this issue one of two ways.
Information/Instructions
Windows 10 - Configuring file association
Press Win + I to open settings (or click the Windows icon and search for Settings) then select System. Now select Default Apps on the left hand side of the window and scroll down to select Choose Default select Choose Default apps by file type.
Now scroll Scroll down until you see .wav on the left hand side. Left-click and then select Windows Media Player. You should now be able to open any .wav files inside of Outlook.
Manually open .wav files in Outlook
Above the main body of the email you should see any attached files, such as voicemails. Click the arrow next to the VoiceMessege and click Open.
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