Microsoft DNS and Macs

Old Network setup
Relied on ISP’s for all DNS services.
New Setup
Installed Microsoft DNS on a NT 4.0 sp6a.
Changed DHCP so that the DNS scope only listed internal DNS.
PC’s work fine. Macs won’t.
Changed DHCP so the the DNS scope has external DNS listed first and internal DNS second. Now the Macs work.
What does it take for the Macs to use the internal Microsoft DNS. Does the NT server that has the Microsoft DNS on it need Services for Macintosh?