_spf.mailer.sendings.email has no MX records.
Question and response
Question
dig _spf.mailer.sendings.email. MX
Answer
The response has no answer records.
Authority
sendings.email. 600 SOA ns13.domaincontrol.com. dns.jomax.net. 2017072700 28800 7200 604800 600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0