Often customers who have VPN clients or even misconfigured internal DNS servers will see their internal hostnames appear in the hostname query report of the Report Center.
In the case of VPN users, when their computer is taken outside of the network it attempts to query their ISP's recursive servers for the same hosts they use internally at work.
If the home domain name is the same as a fully qualified domain name on UltraDNS, the root servers will send the clients to us for resolution even if we don't have the internal records.
These queries will count against your UltraDNS query volume.