_spf.onvol.net has no CNAME records.
Question and response
Question
dig _spf.onvol.net. NS
Answer
The response has no answer records.
Authority
onvol.net. 10800 SOA helium.melitacable.com. domains.melitacable.com. 2025081900 28800 7200 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0