smtp.netanswer.fr has no CNAME records.
Question and response
Question
dig smtp.netanswer.fr. NS
Answer
The response has no answer records.
Authority
netanswer.fr. 35958 SOA ns0.cusae.com. hostmaster.netanswer.fr. 2026022601 7200 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0