v577.v5e5d4d68.usw1.send.mailgun.net has no NS records.
NS records for this zone are defined at v5e5d4d68.usw1.send.mailgun.net.
NS records for this zone are defined at v5e5d4d68.usw1.send.mailgun.net.
Question and response
Question
dig v577.v5e5d4d68.usw1.send.mailgun.net. NS
Answer
The response has no answer records.
Authority
v5e5d4d68.usw1.send.mailgun.net. 300 SOA ns-cloud-a1.googledomains.com. cloud-dns-hostmaster.google.com. 1 21600 3600 259200 300
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0