ns4.serveurcom.com has no CNAME records.
Question and response
Question
dig ns4.serveurcom.com. NS
Answer
The response has no answer records.
Authority
serveurcom.com. 1800 SOA ns1.planet-work.com. nsadmin.planet-work.com. 2602160001 14400 3600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0