When the Preprocess email addresses parameter is selected, all email addresses will be replaced by a special word  __email__ . This will allow a model to learn about email mentions in general rather than from specific email mentions. 

This is particularly useful for excluding email addresses from features (i.e.: using the Preprocess email addresses parameter in combination with the model's stopwords) in cases for which the information encoded in emails is of little value for classification purposes. 

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