mx2.cetelem.com.br has no CNAME records.
Question and response
Question
dig mx2.cetelem.com.br. NS
Answer
The response has no answer records.
Authority
cetelem.com.br. 300 SOA ns1.cetelem.com.br. microinformatica.cetelem.com.br. 1202 7200 3600 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0