mail.nucle.us has one IP number , via cname to smtp.secureserver.net , which also has a corresponding reverse pointer. cblb.net, abate.net, smtp.40.com, bepcusa.com, bnflusa.com and at least 100 other hosts point to the same IP. nucle.us use this as a mailserver. nucle.us is a domain controlled by two nameservers at eunet.rs. They are on the same IP network. Incoming mail for nucle.us is handled by two mailservers at nucle.us themselves. They are on different IP networks. nucle.us has two IP numbers. They are on the same IP network. mail.nucle.us is hosted on a server in United States.