spf6.comodo.com has no CNAME records.
Question and response
Question
dig spf6.comodo.com. NS
Answer
The response has no answer records.
Authority
comodo.com. 2036 SOA ns1.nurd.com. dnsadmin.nurd.com. 172800 60 60 60 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0