I have a SharePoint server that we access internally via a URL. We have established an external IP address for it and opened port 80 through the firewall with a NAT rule to translate from the external IP to the Internal IP of the server. When I type the server URL in my browser, substituting the server name with the external IP it prompts me for a log on as it should, then I get error 404 page cannot be found. If I use the same URL internally, using the server name it logs on normally. Any Ideas?