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Theo has written sa-update – a new script that will be included with SpamAssassin 3.1.0. In theory, we will be able to distribute rules more frequently, and rules releases won't be tied to code releases.
TODO: need more detail here. Ping, Theo!See SaUpdateBackend for details of how this has been implemented.
Scoring
The primary reason for the long release time for new rules is the need to score new rules (and rescore old rules) to generate optimal scores, to flag as much spam as reasonably, while keeping false positives to a conservative minimum.
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