sb.spf.cuenote.jp has no MX records.
Question and response
Question
dig sb.spf.cuenote.jp. MX
Answer
The response has no answer records.
Authority
spf.cuenote.jp. 720 SOA dns1.cuenote.jp. server.ymir.co.jp. 2026012000 28800 14400 604800 720
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0