gw2-1535.security.comendo.com has no MX records.
Question and response
Question
dig gw2-1535.security.comendo.com. MX
Answer
The response has no answer records.
Authority
comendo.com. 3600 SOA ns1.electric.net. dns.electric.net. 1515062461 10000 1800 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0