don57i5udog9x.cloudfront.net has no MX records.
Question and response
Question
dig don57i5udog9x.cloudfront.net. MX
Answer
The response has no answer records.
Authority
don57i5udog9x.cloudfront.net. 900 SOA ns-229.awsdns-28.com. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0