mx.wwwcharter.com has no NS records.
NS records for this zone are defined at wwwcharter.com.
NS records for this zone are defined at wwwcharter.com.
Question and response
Question
dig mx.wwwcharter.com. NS
Answer
The response has no answer records.
Authority
wwwcharter.com. 3600 SOA dns.wwwcharter.com. hostmaster.wwwcharter.com. 1896013136 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0