mx.pulsation.fr has no CNAME records.
Question and response
Question
dig mx.pulsation.fr. NS
Answer
The response has no answer records.
Authority
pulsation.fr. 1448 SOA ns1.celhost.eu. hostmaster.pulsation.fr. 1771840223 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0