[This is preliminary documentation and subject to change.]
The PC97 Designed for Windows logo program requires that new computers have message-waiting indicators on the front of the computer. This enables applications that download e-mail, voice messages, faxes, and other electronic transmissions to indicate to the user that new messages have arrived, even when the system is in the sleeping state. The application calls the SetMessageWaitingIndicator function to update the message-waiting indicator.
The system tracks calls to SetMessageWaitingIndicator on a per-process basis. If a process exits, either normally or abnormally, the system reduces the message-waiting counter by the number of messages specified in the last call the process made to SetMessageWaitingIndicator.