mail.e-start.jp has no CNAME records.
Question and response
Question
dig mail.e-start.jp. NS
Answer
The response has no answer records.
Authority
e-start.jp. 2662 SOA ns8.cpi.ad.jp. hostmaster.cpi.ad.jp. 2026012101 3600 900 3600000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0