spf-mx.directnic.com has no NS records.
NS records for this zone are defined at directnic.com.
NS records for this zone are defined at directnic.com.
Question and response
Question
dig spf-mx.directnic.com. NS
Answer
The response has no answer records.
Authority
directnic.com. 3600 SOA ns1.dnsimple.com. admin.dnsimple.com. 1630574573 86400 7200 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0