ppmx.mailcorp.com.br has no CNAME records.
Question and response
Question
dig ppmx.mailcorp.com.br. NS
Answer
The response has no answer records.
Authority
mailcorp.com.br. 300 SOA dns1.ctitech.net.br. postmaster.ctitech.net.br. 2025111704 28800 3600 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0