E-mail research encompasses a vast and diverse body of work that accumulated over the past 30 years. In this article, we take a critical look at the research literature and ask two simple questions: What is e-mail research? Can it help us reinvent e-mail? Rather than defining an overarching framework, we survey the literature and identify three metaphors that have guided e-mail research up to this day: e-mail as a file cabinet extending human information processing capabilities, e-mail as a production line and locus of work coordination, and, finally, e-mail as a communication genre supporting social and organizational processes. We propose this taxonomy so that designers of future e-mail systems can forge their own direction of research, with knowledge of other directions that have been explored in the past. As an illustration of the possible future work we want to encourage with this review, we conclude with a description of several guidelines for the reinvention of e-mail inspired by our journey through the literature.