_netblocks.sentia.nl has no MX records.
Question and response
Question
dig _netblocks.sentia.nl. MX
Answer
The response has no answer records.
Authority
sentia.nl. 3600 SOA dns1.sentia.dk. hostmaster.sentia.dk. 2025060601 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0