Mark, No knowing what your firewall is I will give you a run down how mine is setup. I have one Exchange 2003 server on my network, a AD-DC, a web server, and a SSL server which are all separate so that they all run on their own boxes. There is info on Microsoft's site on how to install RPC over HTTP on Exchange 2003, to do it on one server like I have you don't need to touch the RPC over HTTP option in Exchange 2003; just leave it alone; you do need to add the RPCProxy registry settings to the Exchange server's reg, and you need to the NDTS settings to the registry on your AD-DC box or box that hands the GC in AD. (don't forget to add the RPC over HTTP component to your Exchange server) You may decide to setup a Split DNS which is usually the best thing to do rather than using the hosts file on your mobile machines. Next if you want your employees to only have access to RPC over HTTP there are tons of tutorials on ISAServer.org on how to setup it up on ISA server, if you are like me and want people to have an option to use either OWA (if they don't have their mobile machine with them) or their mobile machine; RPC over HTTP; you want to get the tutorial that explains how to setup both OWA and RPC over HTTP on one connection in ISA Server. The notes briefly touch base on how to setup RPC, so once you get through it you must create a new mail server publishing rule using the basic web listener and add the /rpc/* to its path. Andrew -----Original Message----- From: Mark Meelhuysen [mailto:m.meelhuysen@xxxxxx] Sent: Saturday, May 14, 2005 1:25 PM To: [ExchangeList] Subject: [exchangelist] Re: RPC over HTTP question http://www.MSExchange.org/ 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.