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Most importantly, you should create a new "bug" entry with the suggested rules in the SpamAssassin bugzilla. This will ensure that the developers will actually see the rules (while the developers participate in the list, it's easy for these suggestions to get lost in the noise). You should attach 1 or more sample spam messages (with all headers intact, please!) as attachments, too, so we can see an example of what the rule is intended to catch.
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