We pick i.root-servers.net, one of the 13 root servers (1), and ask it about clbowa.corelab.com and learn that com is delegated to 13 name servers (2), so we ask l.gtld-servers.net where we learn that corelab.com is delegated to two name servers, including ns1.milw.twtelecom.net (3), so we ask that one where we see a CNAME from clbowa.corelab.com to mail.corelab.com, so we have to start all over again. We already know that ns1.milw.twtelecom.net is authoritative for corelab.com (4) and ask it about mail.corelab.com and get the following answer: