Servidores DNS Principal (mname) y Secundario (rname)
host: 51host.net
class: IN
ttl: 9662
type: SOA
mname: 51host.net
rname: root.51host.net
serial: 2018061214
refresh: 21600
retry: 7200
expire: 604800
minimum-ttl: 3600

Servidor de Correo
host: 51host.net
class: IN
ttl: 78062
type: MX
pri: 10
target: mail.51host.net