> My guess is that gmail is using a linear classifier. Yup, the Google "Priority Inbox" feature does indeed use a linear classifier, in particular logistic reg

> My guess is that gmail is using a linear classifier. Yup, the Google "Priority Inbox" feature does indeed use a linear classifier, in particular logistic regression [1] for the reason of scale as you point out. Also, IIRC Gmail's original spam detection used naive bayes. It may have evolved since then. [1] http://static.googleusercontent.com/media/research.google.com/en/us/pubs/archive/36955.pdf http://static.googleusercontent.com/media/research.google.co...