disk space from deleted messages). Message store The cc:Mail message store is based on a related set of files including a message store file, a directory and index file, and user files. In this structure, multiple users may have a reference in their individual files to the same message, thus the product offered a single instance message store. Message references in user files relate to message offsets stored in an indexed structure. Message offsets refer to locations within the message store file which is common to all users within a given database or "post office". Client technology The cc:Mail system provided native email clients for DOS, Microsoft Windows, OS/2, Macintosh, and Unix (the MIT X Window System under HP-UX and Solaris). cc:Mail allowed client access via native clients, web browsers, POP3 and IMAP4. cc:Mail provided the first commercial web-based email product in 1995. MTA (Router) The cc:Mail MTA or Router, which ran on DOS, 16-bit Windows, Windows NT, and OS/2, supported file access, asynchronous communications, and various network protocols including Novell SPX and TCP/IP. The cc:Mail Router also provided remote access to end users via dial-up and network protocols such as TCP/IP. The "remote call through" feature of the cc:Mail Router made it possible for a mobile user to connect through a single point to access any cc:Mail database within a given cc:Mail system. Various connection types and schedules could be configured along with conditions related to message attributes such as priority or message size to create complex message routing topologies. Gateways The cc:Mail system offered a wide range of email gateways, connectors, and add-on products including links to SMTP, UUCP, IBM PROFS, pager networks, fax, commercial email services such as MCI and more. Directory services cc:Mail provided directory synchronization throughout a system via an Automatic Directory Exchange (ADE) feature which supported a number of 'propagation types', such as peer, superior, and subordinate, from which sophisticated topologies could be constructed. cc:Mail also provided an email-based newsgroup or discussion-like feature referred to as Bulletin Boards which were propagated and synchronized using similar mechanisms. Related features included the ability to synchronize the cc:Mail directory with other directories, such as that of Novell NetWare. Server technology The core cc:Mail technology relied on OSI model network operating systems such as Novell NetWare. These network operating systems provided redirection of native operating system file I/O allowing network nodes to access server-based files transparently, as well