srv1.one.com has one IP number , which also has a corresponding reverse pointer. j1.se, rob.dk, ies.dk, vcs.dk, hfd.dk and at least 100 other hosts point to the same IP. one.com is a domain controlled by two nameservers at b-one-dns.net. They are on the same IP network. Incoming mail for one.com is handled by two mailservers at one.com themselves. They are on the same IP network. one.com has one IP number. srv1.one.com is hosted on a server in Denmark.