mail.a2u2.com has one IP number , which is the same as for a2u2.com, but the reverse is localhost. ns4.de, sunx.org, cabi.net, celox.nl, jcaa.com and at least 100 other hosts point to the same IP. a2u2.com use this as a mailserver. a2u2.com is delegated to two nameservers, however one delegated nameserver is missing in the zone and one other nameserver is listed instead. All nameservers are at cyberlynk.net. All of them are on the same IP network. Incoming mail for a2u2.com is handled by one mailserver at a2u2.com themselves.