iij-dns.net has no MX records.
Question and response
Question
dig iij-dns.net. MX
Answer
The response has no answer records.
Authority
iij-dns.net. 900 SOA ns000.d-53.net. dns-managers.iij.ad.jp. 629 3600 600 604800 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0