mail2.cs.nttpc.info has no CNAME records.
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 1232, xrcode 0, version 0, flags 0