mail.ergos.edu.do has no CNAME records.
Question and response
Question
dig mail.ergos.edu.do. NS
Answer
The response has no answer records.
Authority
ergos.edu.do. 120 SOA ns1.dynu.com. administrator.dynu.com. 66 3600 900 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0