spflive.s4dunning.com has no MX records.
Question and response
Question
dig spflive.s4dunning.com. MX
Answer
The response has no answer records.
Authority
s4dunning.com. 300 SOA ns0.transip.net. hostmaster.transip.nl. 2025121502 86400 1800 2419200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0