scanmx2.sentia.dk has no MX records.
Question and response
Question
dig dk.outbound2.mx25.net. MX
Answer
The response has no answer records.
Authority
mx25.net. 3600 SOA dns1.p01.nsone.net. hostmaster.nsone.net. 1726073215 10000 1800 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0