We pick l.root-servers.net, one of the 13 root servers (1), and ask it about mail.ibit.pu.edu.pk and learn that pk is delegated to three name servers (2), so we ask root-s.pknic.pk where we learn that pu.edu.pk is delegated to four name servers, including xenon.nexlinx.net (3), so we ask that one and get the following answer:
The three mail servers mail, mail1 and mail2.pu.edu.pk together
All of the six domains that use mail server group 1 point only to the IP number 111.68.103.27. Worth noting is that six of the host names that point only to the IP number 111.68.103.27 use mail server group 1.
The mail server mail2.pu.edu.pk
There are six domains that use the mail server mail2.pu.edu.pk.
All of those point only to the IP number 111.68.103.27.
All of them use mail server group 1.
The mail server mail1.pu.edu.pk
There are six domains that use the mail server mail1.pu.edu.pk.
All of those point only to the IP number 111.68.103.27.
All of them use mail server group 1.
The mail server mail.pu.edu.pk
There are six domains that use the mail server mail.pu.edu.pk.
All of those point only to the IP number 111.68.103.27.
All of them use mail server group 1.
The IP number 111.68.103.27 only
There are eleven host names that point only to the IP number 111.68.103.27.
Six of those use mail server group 1. Worth noting is that all of the domains that use mail server group 1 point only to the IP number 111.68.103.27.