Domain name on Win2000 Server

I am using a Windows 2000 Server SBS Server, with 2 clients XP Pro SP3.
I am using the same domain name for the server, as I use for e-mail and Web hotel (for the company web-page)

Before the problem was that I could not connect to our web-page that was previously located at our ISP.
Mail servers were also located at our ISP, but with ISP's own domain name.

Now we have changed web hotel, and both web-page and e-mail server is now located at this web hotel with same domain name as our server.
Now we cannot connect to mail-server, since our network expects to find it on our local server, instead of searching the internet.

Can anyone tell me what settings I should do on our server to redirect this traffic? (Pop, smtp, http, ftp etc)

We have local network inside of the router, with Windows 2000 Servers working as a domain controller. The domain name of this server is the same domain name as web and mail-server that is located externally on the INTERNET. When I try to access webpage from our local computers, I get error message "Page not found". This is because our local server with this domain name, contents no web page. I need to redirect "html, pop, smtp"-traffic to go out on internet.