spf.clicktools.com has no MX records.
Question and response
Question
dig spf.clicktools.com. MX
Answer
The response has no answer records.
Authority
clicktools.com. 300 SOA ns.rackspace.com. hostmaster.rackspace.com. 1647963893 10800 3600 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0