mx.perditionstomb.com has no CNAME records.
Question and response
Question
dig mx.perditionstomb.com. NS
Answer
The response has no answer records.
Authority
perditionstomb.com. 3405 SOA dns.perditionstomb.com. hostmaster.perditionstomb.com. 1411761941 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0