mx.perf1.com has no CNAME records.
Question and response
Question
dig mx.perf1.com. NS
Answer
The response has no answer records.
Authority
perf1.com. 6806 SOA nsa.perf1.fr. technical.nameshield.net. 2026021901 28800 7200 604800 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0