After using the boards for quite a while I found it usefull to register myself :) to actually contribute here.
Anyways After operating a Exchange environment for quite some time we recently deployed RPCoHTTP successfully.
After thoroughly testing on VMWare we decided to move it to an operational status, only I keep running into 1 issue regarding the RPCoHTTPS feature.
The Exchange 2003 server is deployed within the company network, protected by a SonicWall 330PRO and is able to do everything what a normal Exchange server would do.
After setting up several mobile clients (notebooks) to use the RPC proxy the conclusion is that everything works. (from remote locations and via the internal network). Though when accessing a shared calendar via Outlook 2003 from the internal network to the exchange server it produces a NT-Login form to use the domain credentials to access the calendar. If you hit cancel, the previously setup TCP/IP, connection to the exchange server fails and Outlook 2003 goes in offline mode.
It has something to do with the RPC setup, but cannot locate the proper point of failure.