ns01.nttdata.co.jp has no MX records.
Question and response
Question
dig ns01.nttdata.co.jp. MX
Answer
The response has no answer records.
Authority
nttdata.co.jp. 3600 SOA ns01.nttdata.co.jp. postmaster.nttdata.co.jp. 2026012801 3600 1800 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0