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All of the free BL services are enabled by default. However, note that if you're using mail-abuse.org, and you're installing SpamAssassin for site-wide use, you must license their services; mail-abuse.org is now only free for personal use.
FIXME: add a list of non-free tests that are enabled by default so admins can easily disable by setting scores to 0
Note that SpamAssassin still works very well without using these two services, however.
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