smtp-out.byetcluster.com has no MX records.
Question and response
Question
dig smtp-out.byetcluster.com. MX
Answer
The response has no answer records.
Authority
byetcluster.com. 86400 SOA ns1.byet.org. support.byethost.com. 2010111701 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0