cobe.sencinet.com has no MX records.
Question and response
Question
dig cobe.sencinet.com. MX
Answer
The response has no answer records.
Authority
sencinet.com. 1800 SOA rex.ns.cloudflare.com. dns.cloudflare.com. 2396979020 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0