smtp-relay.pbi.net has one IP number , but the reverse is nlpi132.sbcis.sbc.com. nlpi132.sbcis.sbc.com point to the same IP. cta.org, res.net, kcrt.com, emak.com, plcu.com and at least 100 other hosts use this as a mailserver. pbi.net is a domain controlled by two nameservers at pbi.net themselves. They are on the same IP network. Incoming mail for pbi.net is handled by two mailservers having a total of six IP numbers. There are six duplicated IP numbers. Some of them are on the same IP network. smtp-relay.pbi.net is hosted on a server in United States.