I'm an ISP, and mails from our dialups are hitting RCVD_IN_DYNABLOCK.

I have no idea about how to set it up RCVD_IN_DYNABLOCK refers to the Dynablock list, which lists IP addresses that should not be sending mail directly to another server, without passing through a "smarthost" outgoing relay. SpamAssassin gives this a small positive score.

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