mx01.cyon.ch has no CNAME records.
Question and response
Question
dig mx01.cyon.ch. NS
Answer
The response has no answer records.
Authority
cyon.ch. 1060 SOA ns1.cyon.ch. server0.cyon.ch. 2024102205 14400 1800 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0