smtp.supernet.com.bo has no CNAME records.
Question and response
Question
dig smtp.supernet.com.bo. NS
Answer
The response has no answer records.
Authority
supernet.com.bo. 4775 SOA ns.supernet.com.bo. soporte.supernet.com.bo. 2026012800 10800 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0