cf.gmointernet.jp has no MX records.
Question and response
Question
dig cf.gmointernet.jp. MX
Answer
The response has no answer records.
Authority
cf.gmointernet.jp. 1800 SOA moura.ns.cloudflare.com. dns.cloudflare.com. 2395442287 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0