mail2.hull.nu has one IP number , but the reverse is s20.loopia.se. mail2.4e.se, mail2.d8.nu, mail2.etc.se, mail2.llm.se, mail2.upk.se and at least 100 other hosts point to the same IP. hull.nu use this as a mailserver. hull.nu is delegated to two nameservers, however two extra nameservers are listed in the zone. All nameservers are at loopia.se. All of them are on the same IP network. Incoming mail for hull.nu is handled by two mailservers at hull.nu themselves. They are on the same IP network. hull.nu has one IP number. mail2.hull.nu is hosted on a server in Sweden even though the hostname implies Niue.