dk.mx2.mx25.net has no CNAME records.
Question and response
Question
dig dk.mx2.mx25.net. NS
Answer
The response has no answer records.
Authority
mx25.net. 2094 SOA dns1.p01.nsone.net. hostmaster.nsone.net. 1726073215 10000 1800 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0