spf.mailjet.com has no MX records.
Question and response
Question
dig spf.mailjet.com. MX
Answer
The response has no answer records.
Authority
mailjet.com. 180 SOA ns0.mljt.tech. abuse.mailjet.com. 2019314565 14400 900 604800 180
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0