We pick f.root-servers.net, one of the 13 root servers (1), and ask it about j.je and learn that je is delegated to seven name servers (2), so we ask ns99.dns.net.nz where we learn that j.je is delegated to two name servers, including primary-dns.co.uk (3), so we ask that one and get the following answer:
The two name servers primary-dns and secondary-dns.co.uk together
There are more than a thousands domains that use name server group 1.
About one in six of those use mail server group 1 (example: civilandcorporate.co.uk, rele.co.uk and killcoullan.co.uk ). Worth noting is that most of the domains that use mail server group 1 use name server group 1.
The two mail servers tertiary-mx.co.uk and c.secondary-mx.co.uk together
Most of the more than two hundred domains that use mail server group 1 use name server group 1 (example: fatblitz.com, hswestminster.co.uk and adeelmirza.co.uk ). Worth noting is that about one in six of the domains that use name server group 1 use mail server group 1.