Incoming mail for 121.23.62.in-addr.arpa is handled by one mailserver having a total of two IP numbers. They are on the same IP network. idp.fr, kyto.fr, ngset.fr, mgfil.fr, sybex.fr and at least 100 other hosts share mailservers with this domain. 23.62.in-addr.arpa is a domain controlled by three nameservers at colt.net. Two of them are on the same IP network.