mail.ymir.co.jp has no MX records.
Question and response
Question
dig mail.ymir.co.jp. MX
Answer
The response has no answer records.
Authority
ymir.co.jp. 7200 SOA dns1.ymir.co.jp. server.ymir.co.jp. 2026021900 28800 14400 604800 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0