a1v.starfall.com has no MX records.
Question and response
Question
dig d1z1tv13m66uwg.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