Microsoft Exchange Server is a messaging and collaborative software product developed by Microsoft. It is part of the Microsoft Servers line of server products and is widely used by enterprises using Microsoft infrastructure solutions. Exchange's major features consist of electronic mail, calendaring, contacts and tasks; support for mobile and web-based access to information; and support for data storage.

History

Planning the migration from Microsoft's internal "legacy XENIX-based messaging system" to Exchange Server environment began in April 1993 , and by January 1995 some 500 users were running on Exchange Server Beta 1. By April 1996 32,000 users were migrated to the environment.

Exchange Server 4.0, released on June 11, 1996, was the original version of Exchange Server sold to the public, positioned as an upgrade to Microsoft Mail 3.5. The original version of Microsoft Mail (written by Microsoft) had been replaced several weeks after Lotus acquired cc:Mail by a package called Network Courier, acquired during the purchase of Consumer Software Inc. in April 1991. Exchange Server was however an entirely new X.400-based client-server mail system with a single database store that also supported X.500 directory services. The directory used by Exchange Server eventually became Microsoft's Active Directory service, an LDAP-compliant directory server. Active Directory was integrated into Windows 2000 as the foundation of Windows Server domains.

On May 23, 1997, Exchange Server 5.0 was released, which introduced the new Exchange Administrator console, as well as opening up "integrated" access to SMTP-based networks for the first time. Unlike Microsoft Mail (which required a standalone SMTP relay), Exchange Server 5.0 could, with the help of an add-in called the Internet Mail Connector, communicate directly with servers using the internet mail standard. Version 5.0 also introduced a new Web-based e-mail interface Exchange Web Access, this was rebranded as Outlook Web Access in a later Service pack. Along with Exchange Server version 5.0, Microsoft released version 8.01 of Microsoft Outlook, version 5.0 of the Microsoft Exchange Client and version 7.5 of Microsoft Schedule+ to support the new features in the new version of Exchange Server.

Exchange Server 5.5, introduced November, 1997, was sold in two editions, Standard and Enterprise. They differ in database store size, mail transport connectors and clustering capabilities. The Standard Edition had the same 16 GB database size limitation as earlier versions of Exchange Server, while the Enterprise Edition had an increased limit of 16 TB (although Microsoft's best practices documentation recommends that the message store not exceed 100 GB). The Standard Edition includes the Site Connector, MS Mail Connector, Internet Mail Service (previously "Internet Mail Connector"), and Internet News Service (previously "Internet News Connector"), as well as software to interoperate with cc:Mail, Lotus Notes and Novell GroupWise. The Enterprise Edition adds an X.400 connector, and interoperability software with SNADS and PROFS. The Enterprise Edition also introduced two node clustering capability. Exchange Server 5.5 introduced a number of other new features including a new version of Outlook Web Access with Calendar support, support for IMAP4 and LDAP v3 clients and the Deleted Item Recovery feature. Exchange Server 5.5 was the last version of Exchange Server to have separate directory, SMTP and NNTP services. There was no new version of Exchange Client and Schedule+ for version 5.5, instead version 8.03 of Microsoft Outlook was released to support the new features of Exchange Server 5.5.