Apex domains cannot have CNAME records.
Question and response
Question
dig oximailing.com. NS
Answer
oximailing.com. 5 NS ns.oxemis.com.
oximailing.com. 5 NS nssec.online.net.
Authority
The response has no authority records.
Additional
ns.oxemis.com. 5 A 212.83.182.50
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0