mx159.sendpulse.info has no MX records.
Question and response
Question
dig mx159.sendpulse.info. MX
Answer
The response has no answer records.
Authority
sendpulse.info. 10800 SOA a.dns.gandi.net. hostmaster.gandi.net. 1755858785 10800 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0