I have a problem when configuring Outlook with RPC/HTTP. I have an internal exchange 2003 server configured on our domain with the system name "exchange.abc.com". I have registered an mail server with the name of "mail.xyz.com" having a public ip address of "100.100.100.100". This public ip is mapped to our internal mail server through the firewall such as "100.100.100.100" is mapped to "192.168.100.20". OWA works fine from a public network. Now I need to configure outlook to access my exchange server from a public network. I have enabled RPC/HTTP on exchange Server. And i configured RPC/HTTP on outlook for it to be accessed from outside. Now when I enter the mail server as "mail.xyz.com" [External Mail Server] and the username as "John" and when i click on "CHECK NAME", after a long time it finds the username "John" but my Mail Server changes from "MAIL.XYZ.COM" to "EXCHANGE.ABC.COM". That is , it changes the mail server name from external to internal and does not allow Outlook to authenticate. I can see the mail server and username "UNDERLINED" to confirm that it can see the server details. Can you suggest the proper method to configure RPC/HTTP and if there are any DNS Settings that need to be changed?