Why don't my RBLs catch any spam?

[Sam Smith <samtools@xxxxxxxx>]

At least a thousand pieces of spam have reached my mail accounts in the last
24 hrs but the SMTP filter with the standard list hasn't caught one.

Is there some trick to getting them to work. I filled out the form IE
running on OS X 10.3 (i.e., not Safari).

Maybe the spammers are smart enough not to spam from domains on the black
lists.

Thanks

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