dnsdel.mantraonline.com has no NS records.
NS records for this zone are defined at mantraonline.com.
NS records for this zone are defined at mantraonline.com.
Question and response
Question
dig dnsdel.mantraonline.com. NS
Answer
The response has no answer records.
Authority
mantraonline.com. 3600 SOA infoblox.localdomain. please_set_email.absolutely.nowhere. 2013110729 3600 3600 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0