E-mail has become one of the most important communication media for business and private purposes. Large amounts of past e-mail records reside on corporate servers and desktop clients. There is a huge potential for mining this data. E-mail filing and spam filtering are well-established e-mail mining tasks. E-mail filing addresses the assignment of incoming e-mails to predefined categories to support selective reading and organize large e-mail collections. First research on e-mail filing was conducted by Green and Edwards (1996) and Cohen (1996). Pantel and Lin (1998) and Sahami, Dumais, Heckerman, and Horvitz (1998) first published work on spam filtering. Here, the goal is to filter unsolicited messages. Recent research on e-mail mining addresses automatic e-mail answering (Bickel & Scheffer, 2004) and mining social networks from e-mail logs (Tyler, Wilkinson, & Huberman, 2004).