Hi! I have the following network: Internet >> NetscreenFirewall_1 >> ISA 2004 >> NetscreenFirewall_2 >> Internal Network with one Front-End Exchange 2003 server+ one Back-End Exchange 2003 server + one global catalog server. I installed Exchange 2003 SP1 on both Exchnage servers and deployed RPC-HTTP (Front-End/Back-End). On Front-End Exchange I installed RPC Proxy. You know, there is a registry value on RPC Proxy named ValidPorts. Must the port 593 be defined in this registry value? If yes, for which server (for BE? for GC? or for both of them?) Best Regards Mustafa