mail.voce.nl has one IP number , but the reverse is ns1.voce.nl. hdp.nl, b2u.nl, louwes.nl, velzing.nl, mail.hdp.nl and at least 50 other hosts point to the same IP. voce.nl use this as a mailserver. voce.nl is a domain controlled by two nameservers at voce.nl themselves. They are on different IP networks. Incoming mail for voce.nl is handled by three mailservers having a total of four IP numbers. Two of them are on the same IP network. voce.nl has one IP number. mail.voce.nl is hosted on a server in Netherlands.