Apex domains cannot have CNAME records.
Question and response
Question
dig mx1.gib-solutions.ch. NS
Answer
mx1.gib-solutions.ch. 5 NS mx1.gib-solutions.ch.
Authority
The response has no authority records.
Additional
mx1.gib-solutions.ch. 5 A 212.25.8.138
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0