Hi, Anyone give me any advice please as I am puzzled . We have a MS 2000 Exchange server on the DMZ On an Internal 192. address and another group of servers on the internal network with 10. addresses. From the DMZ server we are unable to get DCOM/RPC to work properly to connect to the server on the internal network. We are not using any NAT which I understand can cause DCOM problems. The firewall rule between these two servers is completely unrestricted in both directions. All DCE-RPC groups are allowed as well in a seperate rule. Routing between the two boxes is fine as I can ping in both directions. I do not believe there to be any ACL's in place on network equipment. The smartview logs do not show us blocking any traffic. I don't believe it is a fault with the server on the dmz as if I move it to the Internal network but on a different subnet to the internal server it works fine. I have checked our Exchange boxes and they are all set to use DCOM over TCP/IP as UDP is will not work with win2k and upwards. Exchange and windows server all patched to latest releases Anyone got any ideas? Cheers Phil