spf.braintreegateway.com has no MX records.
Question and response
Question
dig spf.braintreegateway.com. MX
Answer
The response has no answer records.
Authority
braintreegateway.com. 300 SOA ppdns.paypal.com. hostmaster.paypal.com. 2022083747 7200 600 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0