spf01.secure.ne.jp has no MX records.
Question and response
Question
dig spf01.secure.ne.jp. MX
Answer
The response has no answer records.
Authority
secure.ne.jp. 300 SOA ns0.cpi.ad.jp. hostmaster.cpi.ad.jp. 2026021701 3600 900 3600000 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0