mx.mastwall.com has no NS records.
NS records for this zone are defined at mastwall.com.
NS records for this zone are defined at mastwall.com.
Question and response
Question
dig mx.mastwall.com. NS
Answer
The response has no answer records.
Authority
mastwall.com. 3600 SOA dns.mastwall.com. hostmaster.mastwall.com. 1134478552 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0