mail.clicknet.net.br has no CNAME records.
Question and response
Question
dig mail.clicknet.net.br. NS
Answer
The response has no answer records.
Authority
clicknet.net.br. 6141 SOA ns1.clicknet.net.br. noc.clicknet.net.br. 2026020901 3600 120 1209600 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0