ns0.concur.net has no MX records.
Question and response
Question
dig ns0.concur.net. MX
Answer
The response has no answer records.
Authority
concur.net. 14400 SOA dns1.cscdns.net. hostmaster.cscdns.net. 2013021308 28800 7200 604800 14400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0