mails.nuthost.com has no CNAME records.
Question and response
Question
dig mails.nuthost.com. NS
Answer
The response has no answer records.
Authority
nuthost.com. 10710 SOA nut1.nuthost.com. nut1.nuthost.com. 2025042702 86400 7200 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0