ktknet.net has no MX records.
Question and response
Question
dig ktknet.net. MX
Answer
The response has no answer records.
Authority
ktknet.net. 300 SOA ns01.ktk-sol.co.jp. postmaster.ns01.ktk-sol.co.jp. 2024060401 10800 3600 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0