mail.hostserv.ch has no CNAME records.
Question and response
Question
dig mail.hostserv.ch. NS
Answer
The response has no answer records.
Authority
hostserv.ch. 10598 SOA ns1.hostserv.eu. dns.hosttech.eu. 2025041019 7200 120 2419200 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0