mx4.atos.net has no CNAME records.
Question and response
Question
dig mx4.atos.net. NS
Answer
The response has no answer records.
Authority
atos.net. 708 SOA ns1.atos-services.net. ipam.atos.net. 2021122891 900 600 2419200 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0