spf.eco-serv.jp has no MX records.
Question and response
Question
dig spf.eco-serv.jp. MX
Answer
The response has no answer records.
Authority
eco-serv.jp. 300 SOA ns-737.awsdns-28.net. root.eco-serv.jp. 2026022400 3600 900 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0