mail2.mailnbiz.com has no NS records.
NS records for this zone are defined at mailnbiz.com.
NS records for this zone are defined at mailnbiz.com.
Question and response
Question
dig mail2.mailnbiz.com. NS
Answer
The response has no answer records.
Authority
mailnbiz.com. 86400 SOA ns.gabia.co.kr. hosting.gabia.com. 2025041710 1800 600 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0