Here is a crude procmail recipe that I quickly created (NOT a procmail recipe expert, btw) that has been catching lots of spam (current second after the charset_spam recipe posted earlier):
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* .*If.you.do.not.wish.to.receive.[further|additional].[email|mailings].*
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* You.requested.to.receive.this.mailing
more_spam
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* [Uu]nsubscribe|[Oo][Pp][Tt]-[Oo][Uu][Tt]|[Rr]emoved
* [Cc]lick [Hh]ere
* HTML
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OBTW, I think I read somewhere that procmail is not case sensitive within regular expressions and I've tested this and it seems they are not. So, the above can be simplified to:
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* Unsubscribe|Opt-Out|Removed
* Click Here
* HTML
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