_spf.duocast.net has no MX records.
Question and response
Question
dig _spf.duocast.net. MX
Answer
The response has no answer records.
Authority
duocast.net. 3600 SOA ns1.duocast.net. hostmaster.duocast.net. 2026022401 28800 7200 1209600 3600
Additional
. 0 OPT ; payload 1400, xrcode 0, version 0, flags 0