The research program at IBM's® Collaborative User Experience (CUE) group supports an e-mail system used by millions of people. We present three lessons learned from working with real-world enterprise e-mail solutions. First, a pragmatic, system-level approach reveals that e-mail programs are generally used idiosyncratically, often for many different goals at once. This fact has strong implications for both the design and assessment of new features. Second, we discuss how viewing e-mail as an element of corporate collaboration—not just communication—provides insights into problems with current systems as well as potential solutions. Third, we describe constraints imposed by the realities of software development and how they shape the space of feasible new designs. Finally, we illustrate these lessons with an overview of CUE research strategies in the context of an extended case study of one specific new technology: Thread Arcs. Although not all researchers work with an enterprise-level product team, we believe the experiences described here will be useful to anyone wishing to see their ideas ultimately implemented on a broad scale.