Extending the ARPANET technology of an asynchronous, packet-switched "electronic mailbox," the Corporate Information Systems department introduced a pilot mail service within Digital Equipment Corporation which has now grown into a full-fledged production system with some 6,000 users -- and is still growing. The architecture for the Electronic Mail System (EMS) is based on a multinode network of dedicated minicomputers. Technical, administrative and human factors, and cost considerations were recorded throughout the pilot and production period. Lessons learned have highlighted the need for better network engineering, capacity planning, and operational policies/procedures. User surveys were used to capture demographic data and reaffirmed the highly favorable impact on personal productivity and each manager's effectiveness. Recommendations are offered on how to plan for a pilot and to assure a smooth transition to production service.