Selection bias: you don’t see the spam that get rejected at HELO.
My server doesn't reject anyone, but does greylisting. That's a default setting in Postfix. It means the first time an IP address connects it gets a temporary error. If it retries later the message is accepted. That's the only anti-spam measure I have.
Maybe 1 in 5 emails I get is spam, and because I use a different address with every sender I know who sold "my" address to a spam list.
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