This document discusses techniques for filtering spam emails. It begins with an introduction explaining the rise of spam emails due to increased internet and email usage. It then describes various techniques used to filter spam, including machine learning methods like Bayesian classification and non-machine learning methods like blacklists, whitelists, and header analysis. Next, it covers how data mining techniques like clustering, classification, and association rule mining can be applied to identify spam emails. Finally, it reviews several papers that have compared the performance of techniques like Naive Bayes, SVM, KNN, and neural networks for spam filtering.