mail.klausen.dk has no MX records.
Question and response
Question
dig mail.klausen.dk. MX
Answer
The response has no answer records.
Authority
klausen.dk. 600 SOA ns1.klausen.dk. root.klausen.dk. 2019102721 7200 3600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0