Q. What resolver does InterMapper use for its DNS?

A. InterMapper uses two different DNS resolvers. When you add a device using the Insert > Device command, InterMapper uses the system's resolver. When InterMapper is monitoring DNS names and addresses as part of the "DNS Check" feature, InterMapper does its own DNS operations, via UDP packets, to the domain name servers listed in InterMapper's own DNS/WINS settings in the Server Settings. InterMapper's built-in domain name resolver currently assumes that the domain name is fully-qualified. For each domain name, the interval for double-checking the domain name is determined by the TTL in each DNS response (with the minimum interval controlled by the DNS Monitor prefs panel).

When you discover devices, InterMapper initially looks up the FQDN name from the IP address (address --> name), then it settles down to monitoring the domain name (name --> address). InterMapper's built-in DNS resolver doesn't handle partially qualified domain names or things that aren't really domain names; hence, they will fail to resolve.