smtp.tds.cmh.synacor.com has no MX records.
Question and response
Question
dig smtp.tds.cmh.synacor.com. MX
Answer
The response has no answer records.
Authority
synacor.com. 3600 SOA dns1.p05.nsone.net. hostmaster.nsone.net. 1653325585 3600 600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0