_spf.nrtc.syn-alias.com has no CNAME records.
Question and response
Question
dig _spf.nrtc.syn-alias.com. NS
Answer
The response has no answer records.
Authority
syn-alias.com. 121 SOA dns1.p04.nsone.net. hostmaster.nsone.net. 1653399756 3600 600 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0