Polling Exchange for New Mail When Using RPC over HTTPS

When using remote procedure call (RPC) over HTTP Secure (HTTPS), how does Microsoft Office Outlook 2003 determine when new mail is available?

When Outlook runs in Messaging API (MAPI) mode, Exchange Server uses UDP packets on random ports to send new mail notification to the client, as the Microsoft article "XADM: No Way to Configure Port for UDP New Mail Notification Packets" (http://support.microsoft.com/?kbid=264035) describes. However, this approach won't work for RPC-over-HTTPS connections because you tunnel RPC packets over HTTPS so that you don't have to open any additional ports. Instead of using randomly chosen ports for RPC traffic, the Exchange server passes a polling interval to the Outlook client when the server and client first connect and Outlook 2003 polls the server for new mail at that interval. The default interval is set to 60 seconds, but you can change it by creating a new registry entry (of type REG_DWORD) called Maximum Polling Frequency under the HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesMSExchangeISParametersSystem registry subkey, then giving the interval entry the appropriate value in milliseconds.

—Paul Robichaux