mailgun.avolio.tech has no NS records.
NS records for this zone are defined at avolio.tech.
NS records for this zone are defined at avolio.tech.
Question and response
Question
dig mailgun.avolio.tech. NS
Answer
The response has no answer records.
Authority
avolio.tech. 900 SOA ns-794.awsdns-35.net. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0