ns2.x.recruit.co.jp has no MX records.
Question and response
Question
dig ns2.x.recruit.co.jp. MX
Answer
The response has no answer records.
Authority
x.recruit.co.jp. 300 SOA ns1.x.recruit.co.jp. postmaster.x.recruit.co.jp. 2025121600 3600 900 3600000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0