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The SARE Ninjas have a collection of custom rules available at the SpamAssassin Rules Emporium (started by Chris Santerre) - http://www.rulesemporium.com - this collection includes HTML rules, Header abuse rules, ratware rules, specific spammer rules, adult rules, fraud rules, subject rules, business and marketing rules, etc. Several of those rule sets are multi-file rule sets, a practice started by Bob Menschel, allowing you to pick and choose based on the quality or applicability of rules within the MultiFileRuleSets.
The Hebrew SpamAssassin rules project is located at http://www.deltaforce.net/hebrewspam
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