mail01.feeddex.nl has no CNAME records.
Question and response
Question
dig mail01.feeddex.nl. NS
Answer
The response has no answer records.
Authority
feeddex.nl. 136 SOA ns1.shockmedia.nl. hostmaster.shockmedia.nl. 2025051301 10800 1800 345600 43200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0