spf.extole.io has no MX records.
Question and response
Question
dig spf.extole.io. MX
Answer
The response has no answer records.
Authority
extole.io. 900 SOA ns-231.awsdns-28.com. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0