Huge amount of spam not only wastes resources but also brings severe threats to computer system security. To cope with these problems, researchers have conducted extensive researches on anti-spam technologies. This chapter presents the history, current situation, and latest advances in researches on anti-spam technologies in detail. First, this chapter describes and discusses current anti-spam techniques, including legal means, e-mail protocol methods, simple techniques, and intelligent approaches. Then, intelligent anti-spam techniques, which are the most widely used and researched recently, are introduced and analyzed from two aspects: feature extraction approaches and classification methods. After that, performance evaluation methods and benchmark corpora for spam filtering are given. Finally, this chapter summarizes the current anti-spam techniques, and points out the directions of anti-spam researches in the future.