We pick f.root-servers.net, one of the 13 root servers (1), and ask it about rambuspc.com and learn that com is delegated to 13 name servers (2), so we ask c.gtld-servers.net where we learn that rambuspc.com is delegated to four name servers, including udns1.ultradns.net (3), so we ask that one and get the following answer:
Rambuspc.com is a domain controlled by two domain name servers at ultradns.net. Both are on different IP networks. Incoming mail for rambuspc.com is handled by two mail servers at mimecast.com. Both are on different IP networks.