dh.suddenlink.net has no MX records.
Question and response
Question
dig dh.suddenlink.net. MX
Answer
The response has no answer records.
Authority
dh.suddenlink.net. 7200 SOA authns1.alticeusa.net. abuse.alticeusa.com. 2014061701 7200 1800 12096000 7200
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0