smtp.cusae.com has no CNAME records.
Question and response
Question
dig smtp.cusae.com. NS
Answer
The response has no answer records.
Authority
cusae.com. 10792 SOA ns0.cusae.com. hostmaster.cusae.com. 2026022601 43200 7200 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0