mail.srcoop.com.ar has no CNAME records.
Question and response
Question
dig mail.srcoop.com.ar. NS
Answer
The response has no answer records.
Authority
srcoop.com.ar. 10800 SOA srcoop.com.ar. info.srcoop.com.ar. 2026020903 10800 900 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0