_spf.rdstation.com.br has no CNAME records.
Question and response
Question
dig _spf.rdstation.com.br. NS
Answer
The response has no answer records.
Authority
rdstation.com.br. 868 SOA ns-132.awsdns-16.com. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0