mx.zeptomail.jp has no MX records.
Question and response
Question
dig mx.zeptomail.jp. MX
Answer
The response has no answer records.
Authority
zeptomail.jp. 600 SOA ns1.zohocorp.com. dnsadmin.vtitan.com. 2025111503 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0