How can I lock the UDP port that Microsoft Exchange Server uses to notify Microsoft Outlook clients that new mail has arrived?

A. The "New mail" notification that Exchange uses operates over a dynamically assigned UDP port that the Outlook client selects when it first connects to the Exchange server. If you need to lock down this port to enable notification through a firewall, you need to make a client-side registry change (this setting is supported only in Outlook 2003). To do so, create the new DWORD value HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\RPC\FixedUDPPort and set it to the port that the client will listen on for mail notifications. You can find more information about this topic in the Microsoft article "No way to configure port for UDP new mail notification packets" at http://support.microsoft.com/?kbid=264035