_spf.smoothfile.jp has no MX records.
Question and response
Question
dig _spf.smoothfile.jp. MX
Answer
The response has no answer records.
Authority
smoothfile.jp. 60 SOA smoothfile.jp. root.smoothfile.jp. 2026021302 3600 1800 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0