mail1.bigpulse.com has no NS records.
NS records for this zone are defined at bigpulse.com.
NS records for this zone are defined at bigpulse.com.
Question and response
Question
dig mail1.bigpulse.com. NS
Answer
The response has no answer records.
Authority
bigpulse.com. 300 SOA ns1.p201.dns.oraclecloud.net. hostmaster.bigpulse.com. 43 3600 600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0