mx.mtailounie.net has no CNAME records.
Question and response
Question
dig mx.mtailounie.net. NS
Answer
The response has no answer records.
Authority
mtailounie.net. 1800 SOA ns1.neodigit.net. dns.neodigit.net. 1772064000 14400 3600 1209600 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0