mailer6.aremail.com.br has no CNAME records.
Question and response
Question
dig mailer6.aremail.com.br. NS
Answer
The response has no answer records.
Authority
aremail.com.br. 1800 SOA ns1.digitalocean.com. hostmaster.aremail.com.br. 1772197266 10800 3600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0