mx.aol.com is a domain controlled by two nameservers at ns.aol.com. They are on different IP networks. simple.extremeweb.com use this as a mailserver. rr.net, aol.nl, aol.fr, aim.com, aol.com and at least 56 other hosts share nameservers with this domain. mf.mx.aol.com, mb.mx.aol.com, mc.mx.aol.com, xa.mx.aol.com, ma.mx.aol.com and at least 100 other hosts are subdomains to this hostname. aol.com is a domain controlled by four nameservers also at ns.aol.com. All of them are on different IP networks. Incoming mail for aol.com is handled by four mailservers having a total of 14 IP numbers. Some of them are on the same IP network. aol.com has four IP numbers. Two of them are on the same IP network.