mx.as2.ch has no CNAME records.
Question and response
Question
dig mx.as2.ch. NS
Answer
The response has no answer records.
Authority
as2.ch. 5777 SOA ns1.as2.ch. info.as2.ch. 2025112101 10800 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0