smtp2.idc.jp has no CNAME records.
Question and response
Question
dig smtp2.idc.jp. NS
Answer
The response has no answer records.
Authority
idc.jp. 600 SOA ns01.idc.jp. dns-support.idc.jp. 2016080999 10800 1800 3600000 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0