5367455.spf06.hubspotemail.net has no MX records.
Question and response
Question
dig 5367455.spf06.hubspotemail.net. MX
Answer
The response has no answer records.
Authority
spf06.hubspotemail.net. 180 SOA ns10.digicertdns.com. dns.digicertdns.com. 2009010104 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0