smtp.mls.com.br has no CNAME records.
Question and response
Question
dig smtp.mls.com.br. NS
Answer
The response has no answer records.
Authority
mls.com.br. 3366 SOA ns.mls.com.br. admin.mls.com.br. 2026020902 10800 3600 3600000 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0