ns3.domainnetwork.com has no MX records.
Question and response
Question
dig ns3.domainnetwork.com. MX
Answer
The response has no answer records.
Authority
domainnetwork.com. 86400 SOA udns1.cscdns.net. hostmaster.cscdns.net. 2013080840 14400 3600 2419200 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0