mx.directnic.net has no NS records.
NS records for this zone are defined at directnic.net.
NS records for this zone are defined at directnic.net.
Question and response
Question
dig mx.directnic.net. NS
Answer
The response has no answer records.
Authority
directnic.net. 3600 SOA ns1.dnsimple.com. admin.dnsimple.com. 1630476119 86400 7200 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0