ns.digsys.bg has one IP number , which also has a corresponding reverse pointer. hbo.bg, brg.bg, ntz.bg, nic.bg, b2b.bg and at least 100 other hosts use this as a nameserver. register.bg use this as a mailserver. digsys.bg is a domain controlled by two nameservers at digsys.bg themselves. They are on different IP networks. Incoming mail for digsys.bg is handled by two mailservers also at digsys.bg. They are on different IP networks. ns.digsys.bg is hosted on a server in Bulgaria.