mx.expedient.net has no NS records.
NS records for this zone are defined at expedient.net.
NS records for this zone are defined at expedient.net.
Question and response
Question
dig mx.expedient.net. NS
Answer
The response has no answer records.
Authority
expedient.net. 3600 SOA auth1.dns.expedient.com. hostmaster.expedient.com. 2013073101 3600 900 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0