We pick k.root-servers.net, one of the 13 root servers (1), and ask it about altavistaeurope.org and learn that org is delegated to six name servers (2), so we ask d0.org.afilias-nst.org where we learn that altavistaeurope.org is delegated to five name servers, including ns3.yahoo.com (3), so we ask that one and get the following answer:
The five name servers ns1, ns2, ns3, ns4 and ns5.yahoo.com together
Three quarter of the several hundred of domains that use name server group 1 point to the two IP numbers 68.180.206.184 and 98.139.102.145 together, hereafter referred to as "IP group 1", (example: cgi2-yahoo.com, dlsyahoo.com and emailyahoomail.com ). Worth noting is that most of the host names that point to IP group 1 use name server group 1.
The mail server. Only
There are more than hundred domains that only use the mail server ..