mx.beepweb.net has no CNAME records.
Question and response
Question
dig mx.beepweb.net. NS
Answer
The response has no answer records.
Authority
beepweb.net. 1688 SOA ns0.beepweb.net. hostmaster.beepweb.net. 2025082801 3600 900 1209600 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0