mail.desktop.com.br has no CNAME records.
Question and response
Question
dig mail.desktop.com.br. NS
Answer
The response has no answer records.
Authority
desktop.com.br. 600 SOA dns1.desktop.com.br. sysop.desktop.com.br. 2026021105 10800 1800 2592001 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0