The War Against Spam: A report from the front line

Fighting spam is a success story of real-world machine learning. Despite the occasional spam that does reach our inboxes, the overwhelming majority of spam —
and there is a lot of it — is positively identified. At the same time, the rarity with which users feel the need to check their spam box for false positives demonstrates
a high precision of classification. This paper is an overview of Google’s approach to fighting email abuse with machine learning, and a discussion of some lessons learned.

• Machine Intelligence