dc3.bigmachines.com has no MX records.
Question and response
Question
dig dc3.bigmachines.com. MX
Answer
The response has no answer records.
Authority
bigmachines.com. 300 SOA ns1.p201.dns.oraclecloud.net. hostmaster.bigmachines.com. 2020129533 3600 600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0