I also have a question about this option. When I want to use Exchange over http, do I need to open any extra ports on my firewall? Besides port 80 ofcourse. And how do I configure RPC over http on my exchange server exactly. At this moment my server is "not part of an exchange managed RPC-HTTP topology" and when I select "RPC-HTTP back-end server" I get the warning: "There is no RPC-HTTP front-end in your Exchange organisation". I think I understand what the warming means and why. So now my question is: Is it possible to accomplisch my goal with just one Exchange 2003 server in my organisation which is also my DC, webserver, fileserver? It is separated from the internet by an other machine who has only the function of a firewall and that is not part of the domain.