mail.ecom.net.do has no CNAME records.
Question and response
Question
dig mail.ecom.net.do. NS
Answer
The response has no answer records.
Authority
ecom.net.do. 936 SOA ns1.ecom.net.do. webmaster.ecom.net.do. 2026021800 3600 600 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0