mail2.dc.ctc.ad.jp has no MX records.
Question and response
Question
dig mail2.dc.ctc.ad.jp. MX
Answer
The response has no answer records.
Authority
dc.ctc.ad.jp. 300 SOA ns0.dc.ctc.ad.jp. root.dc.ctc.ad.jp. 2025101701 28800 7200 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0