Small business server 4.5

I have small business server 4.5 installed on my server with proxy 2.0, nt 4.0 service pack 4 and exchange server 5.5. I recently had a web site designed however when I tpye the web address ex. http://www.example.com it redirects me to a site to register the domain. I checked the dns setting on the server for host and domin and it has the domain listed. When I try to view the web outsite of the firewall it works find. It seem like there is a DNS problem. Please help.

Thanks,

Craig