spf12.sphere.ad.jp has no MX records.
Question and response
Question
dig spf12.sphere.ad.jp. MX
Answer
The response has no answer records.
Authority
spf12.sphere.ad.jp. 3600 SOA ns1.sphere.ad.jp. mail=dns.sphere.ad.jp. 2025052101 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0