mail.edgetelecom.com.br has no CNAME records.
Question and response
Question
dig mail.edgetelecom.com.br. NS
Answer
The response has no answer records.
Authority
edgetelecom.com.br. 300 SOA ns.edgetelecom.com.br. root.edgetelecom.com.br. 2017010228 10800 3600 2419200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0