mx.amccumn.com has no NS records.
NS records for this zone are defined at amccumn.com.
NS records for this zone are defined at amccumn.com.
Question and response
Question
dig mx.amccumn.com. NS
Answer
The response has no answer records.
Authority
amccumn.com. 3600 SOA dns.amccumn.com. hostmaster.amccumn.com. 1211286362 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0