Inter-organizational projects involve the creation, modification and management of content. Unless carefully handled, these overheads can came the loss of mutual understanding. In this paper, we propose a content management approach for inter-organizational projects that uses the e-mail metaphor; the functions of creating, modifying, and managing content are represented as e-mail messages that are sent to project members automatically. The e-mail metaphor allows us to communicate the creation, modification and management of content explicitly across organizations. It promotes mutual understanding in interorganizational projects. We have developed a content management system that uses the e-mail metaphor. When one project member adds content to the project, the system informs this event to the other project members. When the project manager manages the content by grouping, commenting or semantic annotation, the system informs to project members of the operation by e-mail metaphor such as creating a mailbox for a new group.