spam.virtuoso.com has two IP numbers. They are on the same IP network. nctw.com, tc-m.com, liadis.com, madpoo.com, melroy.com and at least 100 other hosts use this as a mailserver. virtuoso.com is delegated to one nameserver, however two extra nameservers are listed in the zone. All nameservers are at virtuoso.com themselves. All of them are on different IP networks. Incoming mail for virtuoso.com is handled by one mailserver having a total of two IP numbers. They are on the same IP network. virtuoso.com has one IP number. spam.virtuoso.com is hosted on two servers in United States.