In essence this is one of the principles, the thing is the emails don't need to be perfectly identical, just identical-ish with the identicalish matching implementation being not public (as this would immediately lead to spammers adding just enough randomness to whatever they are sending)
Re:The “mail is hard” myth
by al_form2000 on Sunday September 01, 2019 @03:55PM
(#20854444)
In short, no.
Wait, is this really the way how spam filters work? All I need to do is to add a random number to all emails to bypass spam filters?