Where do you configure the DNS server IP address in OpUtiils5?

I found one place under IP Address Manager -> Settings where it calls for a "DNS Server Name" (wouldn't you need the IP address, though, not the name? How is it going to find resolve the name without a DNS server?). I've set that to the IP address of my machine running OpUtils5, since that machine is also running SimpleDNSPro. I can resolve local names and IP addresses via NSLOOKUP from a DOS Window, but the OpUtils5 reports and other things don't resolve private IP addresses to names, despite their being in-addr zones for all my private IPs in my name servers. It will, however, resolve external things like www.mit.edu. What is it using for DNS server and where can I change that?

-mel