delete messages where "the sender is not permitted"
There are many spams where in the header states "the domain of xxxxx.com does not designate ... as permitted sender"
DELETE those messages instead of sending them to the "Spam" folder!
This would eliminate all those SPAMS with FORGED headers!
1st
ranked

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Edwin Hampton commented
Here are Four examples of SPAM received on Sept 01
Return-Path: <ReturnEqqC57ou3b@gandi.net>
Return-Path: <ReturnOK7h75q6v4@gandi.net>
Return-Path: <ReturnbPHR2hDcdr@gandi.net>
Return-Path: <ReturnNnVYlujXf8@gandi.net>
In ALL four examples, the sender had FORGED the sending address, because the header said
"(domain of gandi.net does not designate 80.211.179.118 as permitted sender)"