mx.rotofiles.com has no CNAME records.
Question and response
Question
dig mx.rotofiles.com. NS
Answer
The response has no answer records.
Authority
rotofiles.com. 3414 SOA dns.rotofiles.com. hostmaster.rotofiles.com. 1244793483 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0