Servidores DNS Principal (mname) y Secundario (rname)
host: csdb.cn
class: IN
ttl: 7200
type: SOA
mname: ns.sdb.ac.cn
rname: root.ns.sdb.ac.cn
serial: 2018111954
refresh: 10800
retry: 3600
expire: 360000
minimum-ttl: 7200

Servidor de Correo
host: csdb.cn
class: IN
ttl: 7200
type: MX
pri: 10
target: mx.cstnet.cn