mx4.spamfri.dk has no CNAME records.
Question and response
Question
dig mx4.spamfri.dk. NS
Answer
The response has no answer records.
Authority
spamfri.dk. 1123 SOA ns1.dns.services. post.dns.services. 2022051769 10800 3600 1814400 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0