www.mlist.bri.or.jp has no MX records.
Question and response
Question
dig www.mlist.bri.or.jp. MX
Answer
The response has no answer records.
Authority
bri.or.jp. 3600 SOA asns1.customer.ne.jp. yokoya.bri.or.jp. 1551759721 3600 1800 3628800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0