This study examines how employees in a distributed work group use email copies in networks of collaboration. It studies the audience design of messages with multiple recipients, analyzing explicit and implicit addressing devices used to appoint recipients as primary and secondary participants in the interaction. Copying in recipients serves to share knowledge of ongoing projects and to build up a common information pool. Furthermore, it is used to facilitate multi-party interaction and to build personal identity and alliances. Copies to third parties may also be used for reasons of social control, for instance in order to gain compliance or to put pressure on the addressee to conform to social norms of conduct.