smtp-dev.rumahweb.net has no CNAME records.
Question and response
Question
dig smtp-dev.rumahweb.net. NS
Answer
The response has no answer records.
Authority
rumahweb.net. 1411 SOA dns3.cloudns.net. support.cloudns.net. 2026022304 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0