I have received this error using OL2003 SP2 connecting via RPC thru HTTPS to Exchange 2003 SP2 Server. My firewall allows port 80, 443 and 444 to my server. I have tested my RPC/HTTPS OL2003 config in the office with success. My external tests have no proxy or firewall intervention from the sites that I have used. Logon seems to complete fine but the error occurs at Send/Recieve call.