b.spf.163.com has no CNAME records.
Question and response
Question
dig b.spf.163.com. NS
Answer
The response has no answer records.
Authority
163.com. 60 SOA ns4.nease.net. admin.nease.net. 20292016 7200 1800 1209600 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0