Configure DHCP, DNS and AD on Windows 2012

Hi, I have installed windows 2012 server to act as the following: 1. DNS 2. DHCP 3. Active Directory 4. Exchange Server The client PC's are being assigned dynamic IP's and identifying the server as the DNS. On the other hand, the nslookup is not properly resolving the host names. Additionally, I am not able to join the PC's to the domain (the same server). Doing NSLOOKUP on the server returns the same error and does not take itself as the default DNS. We are looking for a service provider who can complete the configuration and correct those small issues. Regards, Aziz