spf2.sakura.ad.jp has no MX records.
Question and response
Question
dig spf2.sakura.ad.jp. MX
Answer
The response has no answer records.
Authority
sakura.ad.jp. 3600 SOA dns.sakura.ad.jp. noc.sakura.ad.jp. 2026021802 3600 900 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0