mxplan4.mail.ovh.net has no CNAME records.
Question and response
Question
dig mxplan4.mail.ovh.net. NS
Answer
The response has no answer records.
Authority
mail.ovh.net. 60 SOA dns10.ovh.net. tech.ovh.net. 2026030215 86400 3600 3600000 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0