mx.inboxed3.com has no CNAME records.
Question and response
Question
dig mx.inboxed3.com. NS
Answer
The response has no answer records.
Authority
inboxed3.com. 3355 SOA dns.inboxed3.com. hostmaster.inboxed3.com. 1954959806 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0