mx.arubacloud.fr has no CNAME records.
Question and response
Question
dig mx.arubacloud.fr. NS
Answer
The response has no answer records.
Authority
arubacloud.fr. 156 SOA arudns1.aruba.it. hostmaster.aruba.it. 2026021203 86400 7200 2592000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0