Hi,
I'm assuming that you've got the DUC client component installed and have updated your mail file design. Otherwise you would see errors.
On the little player/recorder control that is displayed when you open a voice message, there's a little icon of a phone and a little icon of a computer. Underneath that there are two options with radio buttons labled "Recording" and "Playback". If you click the radio button underneath the icon of the computer, message playback is done via the speakers on your computer. If you click the radio button underneath the phone icon and enter your phone number, playback of the message is done via the phone.
Playback/recording by phone is a bit complex. Notes passes the phone number to Unity, and Unity does the dial out using the phone system that is integrated with Unity. So there are more than likely limitations on which phone numbers will work in this field.
When you open an existing voice message, the record button is inactive. When click the menu item New > Voice Message, the record button should be active. The record button should also be active when you choose the menu items Voice Reply or Forward > Voice.
Nancy