Windows 2003

I have a windows server 2003 small business server. I have installed a single domain (abc.com) active directory on my internal network. My DNS server is configured to forward queries to the ISP’s DNS server for names it can’t resolve. My DNS server successfully resolves all external names but not external abc.com names such as www.abc.com (web site hosted by a third party host) or pop.abc.com (pop server hosted by third party mail host). can anyone help.