b._spf.mailer.airtel.com has no NS records.
NS records for this zone are defined at mailer.airtel.com.
NS records for this zone are defined at mailer.airtel.com.
Question and response
Question
dig b._spf.mailer.airtel.com. NS
Answer
The response has no answer records.
Authority
mailer.airtel.com. 900 SOA infoblox.localdomain. please_set_email.absolutely.nowhere. 184 10800 3600 2419200 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0