smtp.bytetrust.net has no CNAME records.
Question and response
Question
dig smtp.bytetrust.net. NS
Answer
The response has no answer records.
Authority
bytetrust.net. 3600 SOA dns12.ovh.net. tech.ovh.net. 2026022709 86400 3600 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0