mx-mail39.airtel.com has no NS records.
NS records for this zone are defined at airtel.com.
NS records for this zone are defined at airtel.com.
Question and response
Question
dig mx-mail39.airtel.com. NS
Answer
The response has no answer records.
Authority
airtel.com. 86400 SOA dnsdel.mantraonline.com. root.dnsdel.mantraonline.com. 2014073124 7200 3600 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0