spf4.exacttarget.com has no CNAME records.
Question and response
Question
dig spf4.exacttarget.com. NS
Answer
The response has no answer records.
Authority
exacttarget.com. 56 SOA dns1.p01.nsone.net. hostmaster.nsone.net. 1682536669 7200 3600 1209600 21600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0