mx.ovh.com has no CNAME records.
Question and response
Question
dig mx.ovh.com. NS
Answer
The response has no answer records.
Authority
ovh.com. 472 SOA dns.ovh.net. tech.ovh.net. 2026022099 86400 3600 3600000 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0