mail2.cs.nttpc.info has no NS records.
NS records for this zone are defined at cs.nttpc.info.
NS records for this zone are defined at cs.nttpc.info.
Question and response
Question
dig mail2.cs.nttpc.info. NS
Answer
The response has no answer records.
Authority
cs.nttpc.info. 300 SOA ns-518.awsdns-00.net. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0