smtp.dcarsat.com.ar has no CNAME records.
Question and response
Question
dig smtp.dcarsat.com.ar. NS
Answer
The response has no answer records.
Authority
dcarsat.com.ar. 3554 SOA ns1.dcarsat.com.ar. nsadmin.dcarsat.com.ar. 2020012958 10800 3600 604800 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0