mx.donnasoldmine.com has no CNAME records.
Question and response
Question
dig mx.donnasoldmine.com. NS
Answer
The response has no answer records.
Authority
donnasoldmine.com. 3198 SOA dns.donnasoldmine.com. hostmaster.donnasoldmine.com. 1846393325 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0