k135.k5ca2bed.use4.send.mailgun.net has no NS records.
NS records for this zone are defined at k5ca2bed.use4.send.mailgun.net.
NS records for this zone are defined at k5ca2bed.use4.send.mailgun.net.
Question and response
Question
dig k135.k5ca2bed.use4.send.mailgun.net. NS
Answer
The response has no answer records.
Authority
k5ca2bed.use4.send.mailgun.net. 300 SOA ns-cloud-d1.googledomains.com. cloud-dns-hostmaster.google.com. 1 21600 3600 259200 300
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0