c30.c09224bb.usw1.send.mailgun.net has no NS records.
NS records for this zone are defined at c09224bb.usw1.send.mailgun.net.
NS records for this zone are defined at c09224bb.usw1.send.mailgun.net.
Question and response
Question
dig c30.c09224bb.usw1.send.mailgun.net. NS
Answer
The response has no answer records.
Authority
c09224bb.usw1.send.mailgun.net. 300 SOA ns-cloud-e1.googledomains.com. cloud-dns-hostmaster.google.com. 1 21600 3600 259200 300
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0