mx4.nexicom.net has no CNAME records.
Question and response
Question
dig mx4.nexicom.net. NS
Answer
The response has no answer records.
Authority
nexicom.net. 600 SOA mail.nexicom.net. root.nexicom.net. 2026030603 3600 600 1209600 800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0