mx0.charter.net has no CNAME records.
Question and response
Question
dig mx0.charter.net. NS
Answer
The response has no answer records.
Authority
charter.net. 3016 SOA ns1.charter.com. hostmaster.charter.com. 2025060009 43200 3600 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0