mail.nipaads.com has no CNAME records.
Question and response
Question
dig mail.nipaads.com. NS
Answer
The response has no answer records.
Authority
nipaads.com. 1588 SOA rosemary.ns.cloudflare.com. dns.cloudflare.com. 2395565441 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0