v581.v5e1473f2.use4.send.mailgun.net has no NS records.
NS records for this zone are defined at v5e1473f2.use4.send.mailgun.net.
NS records for this zone are defined at v5e1473f2.use4.send.mailgun.net.
Question and response
Question
dig v581.v5e1473f2.use4.send.mailgun.net. NS
Answer
The response has no answer records.
Authority
v5e1473f2.use4.send.mailgun.net. 300 SOA ns-cloud-b1.googledomains.com. cloud-dns-hostmaster.google.com. 1 21600 3600 259200 300
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0