mx.topbrandca.com has no NS records.
NS records for this zone are defined at topbrandca.com.
NS records for this zone are defined at topbrandca.com.
Question and response
Question
dig mx.topbrandca.com. NS
Answer
The response has no answer records.
Authority
topbrandca.com. 3600 SOA dns.topbrandca.com. hostmaster.topbrandca.com. 1506819461 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0