Re:Just Use Email – How to Use Email for Everything
by habibur on Wednesday May 12, 2021 @04:59AM
(#27128223)
SPF will pass if there is no SPF record in the domain. Which most probably is the case for most.
Look for DKIM. Either it's signed and pass. Or spam if DKIM is missing. You can filter a lot more this way.
Quick look at my archive, of 37k spams only 7k fails SPF. (I accept all email no matter what.) So it's some signal, but not nearly enough.