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The auto-whitelist, or AWL, tracks scores for your regular correspondents in a small on-disk database. In 3.1, it is a plugin, loaded by default in the file v310.pre. In 3.0, it is enabled by default and turned off with the configuration setting use_auto_whitelist 0. In earlier versions, it is enabled using the -a flag to spamassassin or spamd.
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