We pick i.root-servers.net, one of the 13 root servers (1), and ask it about bolux.bw and learn that bw is delegated to seven name servers (2), so we ask ns.uu.net where we learn that bolux.bw is delegated to two name servers, including opqns2.opqnet.net (3), so we ask that one and get the following answer:
Bolux.bw is a domain controlled by two domain name servers at opqnet.net. Both are on the same IP network. Incoming mail for bolux.bw is handled by three mail servers also at opqnet.net. All three of them are on the same IP network.
Most of them use the three mail servers mx1, mx2 and mx3.opqnet.net together, hereafter referred to as "mail server group 1", (example: ogilvy.co.bw, itibots.com and mast.co.bw ). Worth noting is that most of the domains that use mail server group 1 use name server group 1.