|You can use your Local DNS server to resolve local IP's but for it to provide resolution outside the local zone you have to enable forwarding on it. In order to make this work, enable forwarding on the DNS server and have your clients point to the internal DNS server. |
You may encounter problems connecting internally to your web site or possibly externally as well if you change your present DNS configuration. So be aware of that before you begin making changes. I'm not web site admin so hopefully someone else will come along that will be better equipped to help you. But I do have plenty of experience installing/maintaining servers and domains and the above is the preferred method for configuring DNS within a domain.
You could help us help you by telling us how your DNS is presently configured.