mx.mailsecurity.fr has no CNAME records.
Question and response
Question
dig mx.mailsecurity.fr. NS
Answer
The response has no answer records.
Authority
mailsecurity.fr. 125 SOA ns1.webaxys.net. hostmaster.webaxys.net. 2024011506 7200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0