ns1.open.by has one IP number , but the reverse is a.open.by. a.open.by and mail.greenexpo.by point to the same IP. by, kp.by, te.by, 3s.by, tp.by and at least 100 other hosts use this as a nameserver. open.by is a domain controlled by four nameservers. Two of them are on the same IP network. Incoming mail for open.by is handled by one mailserver at open.by themselves. open.by has one IP number. ns1.open.by is hosted on a server in Belarus.