support.efscloud.net has no MX records.
Question and response
Question
dig dnoy5gxjrd92x.cloudfront.net. MX
Answer
The response has no answer records.
Authority
cloudfront.net. 60 SOA ns-418.awsdns-52.com. hostmaster.cloudfront.net. 1377556270 16384 2048 1048576 60
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0