mail.icss.edu.do has no CNAME records.
Question and response
Question
dig mail.icss.edu.do. NS
Answer
The response has no answer records.
Authority
icss.edu.do. 180 SOA ns0.dnsmadeeasy.com. dns.dnsmadeeasy.com. 2008010116 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0