When I receive a message which is marked with high priority, Outlook plays 3 loud beeps.
How can I disable this?
The 3 loud beeps are probably caused by the Cisco Unity ViewMail add-in. You can disable this option (without affecting any other functionality of the Cisco utility) via;
Tools-> ViewMail Options…-> tab Notification
Here you can also disable the “You have voice mail” notification.
If you actually like this kind of notification but you don’t have the Cisco Unity ViewMail add-in, then you could still create a rule to play a specific sound when a message with high priority comes in. You can basically select any wav-file for this.
Note: If you get a beep sound for each message that comes in, then take a look here.