mail.satserver.nl has no CNAME records.
Question and response
Question
dig mail.satserver.nl. NS
Answer
The response has no answer records.
Authority
satserver.nl. 7200 SOA ns1.satserver.nl. hostmaster.satserver.nl. 2026030402 28800 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0