cc:Mail is a discontinued store-and-forward LAN-based email system originally developed on Microsoft's MS-DOS platform by Concentric Systems, Inc. in the 1980s. The company, founded by Robert Plummer, Hubert Lipinski, and Michael Palmer, later changed its name to PCC Systems, Inc., and then to cc:Mail, Inc. At the height of its popularity, cc:Mail had about 14 million users, and won various awards for being the top email software package of the mid-1990s. Architecture overview In the 1980s and 1990s, it became common in office environments to have a personal computer on every desk, all connected via a local area network (LAN). Typically, (at least) one computer is set up as a file server, so that any computer on the LAN can store and access files on the server as if they were local files. cc:Mail was designed to operate in that environment. The central point of focus in the cc:Mail architecture is the cc:Mail "post office," which is a collection of files located on the file server and consisting of the message store and related data. However, no cc:Mail software needs to be installed or run on the file server itself. The cc:Mail application is installed on the user desktops. It provides a user interface, and reads and writes to the post office files directly in order to send, access, and manage email messages. This arrangement is called a "shared-file mail system" (which was also implemented later in competing products such as Microsoft Mail). This is in contrast to a "client/server mail system" which involves a mail client application interacting with a mail server application (the latter then being the focal point of message handling). Client/server mail was added later to the cc:Mail product architecture (see below), and also became available in competing offerings (such as Microsoft Exchange). Other than the cc:Mail desktop application, key software elements of the cc:Mail architecture include cc:Mail Router (for transferring messages between post offices, possibly in distant locations, and for providing a dial-in access point for users using the mobile version of the cc:Mail desktop application), gateways (providing links to other mail system types), and various administrative tools. Like the cc:Mail desktop application, all of these can access the post office via the file-sharing facility of the local area network. However, some administrative functions required exclusive access to the post office, so post offices would be taken offline periodically for necessary maintenance (such as recovering