b.spf.comendo.com has no MX records.
Question and response
Question
dig b.spf.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