smtp.anet.dk has no CNAME records.
Question and response
Question
dig smtp.anet.dk. NS
Answer
The response has no answer records.
Authority
anet.dk. 10800 SOA ns01.athena-hosting.dk. hostmaster.athena-hosting.dk. 2021032402 86400 7200 86400 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0