mail.mrse.com.ar has no CNAME records.
Question and response
Question
dig mail.mrse.com.ar. NS
Answer
The response has no answer records.
Authority
mrse.com.ar. 3958 SOA dns1.mrse.com.ar. tasamail.telefonica.com.ar. 2025011012 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0