ool-4579d0fa.dyn.optonline.net has no MX records.
Question and response
Question
dig ool-4579d0fa.dyn.optonline.net. MX
Answer
The response has no answer records.
Authority
dyn.optonline.net. 86400 SOA authns1.cv.net. hostmaster.cv.net. 2012040290 7200 600 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0