mx.interlink.or.jp has no CNAME records.
Question and response
Question
dig mx.interlink.or.jp. NS
Answer
The response has no answer records.
Authority
interlink.or.jp. 3186 SOA dns1.interlink.or.jp. root.dns1.interlink.ad.jp. 2026020601 86400 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0