mx.sprintdatacenter.net has no CNAME records.
Question and response
Question
dig mx.sprintdatacenter.net. NS
Answer
The response has no answer records.
Authority
sprintdatacenter.net. 3600 SOA ns1.sprintdatacenter.net. hostmaster.sprintdatacenter.net. 2019053001 86400 7200 2419200 604800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0