Sentiment is a rich and important dimension of social interaction. However, its presence in computer-mediated communication in corporate settings is not well understood. This paper provides a preliminary study of people's expression of sentiment in email conversations in an organizational context. The study reveals that sentiment levels evolve over time during the process of newcomers' socialization, that sentiment varies according to tie-strength with the recipient, and that sentiment patterns can be indicative of one's position in the corporate social network as well as job performance. These findings shed light on the complex and dynamic nature of sentiment patterns, and would inspire further explorations and applications of sentiment analysis in organizations. Copyright 2012 ACM.