mail.satel.fr has no CNAME records.
Question and response
Question
dig mail.satel.fr. NS
Answer
The response has no answer records.
Authority
satel.fr. 5298 SOA ns0.eolas.fr. hostmaster.eolas.fr. 138 86400 7200 1209600 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0