_netblocks1.conoha.ne.jp has no MX records.
Question and response
Question
dig _netblocks1.conoha.ne.jp. MX
Answer
The response has no answer records.
Authority
conoha.ne.jp. 3600 SOA ns-a1.conoha.io. postmaster.conoha.ne.jp. 1771575662 3600 600 86400 3600
Additional
. 0 OPT ; payload 2800, xrcode 0, version 0, flags 0