Windows Server 2012 R2 Essentials is the previous version of Windows Server Essentials designed for small businesses with up to 25 users and 50 devices.
Windows Server 2012 R2 Essentials can also be used as the primary server in a multi-server environment for small businesses.
Exchange database size limit is set to 18 GB by default but can be expanded to 75 GB using a registry key.
Consists of Windows Server 2008 and includes Microsoft Exchange Server 2007, Windows Share Point Services 3.0 and 120-day trial subscriptions of new security products from Microsoft, namely, Forefront Security for Exchange and Windows Live One Care for Server.
Consists of Windows NT Server 4.0 SP4 and includes Exchange Server 5.5 SP2, IIS 4.0, SQL Server 7.0, Proxy Server 2.0, Internet Explorer 5.0, Outlook 2000, and Front Page 2000; allows 50 client licenses.
Consists of Windows 2000 Server (including Internet Explorer 5.0 and IIS 5.0) and includes Exchange 2000 Server, SQL Server 2000 Standard Edition, Internet Security & Acceleration Server 2000, Outlook 2000 and Front Page 2000; allows 50 client licenses.
Windows Small Business Server (not Essentials) had its own type of CAL, and included the user CALs for Windows Server, Exchange Server, and eventually SQL Server; the SBS CAL cost more than the Windows Server license, but less than the sum of separate access licenses for the two or three servers.
Whereas formerly, the premium edition of SBS was packaged as a superset of the standard edition, in the 2011 wave it will be available as an add-on edition, containing standalone copies of SQL Server 2008 R2 and Windows Server 2008 R2, and available to add onto either SBS 2011 Essentials or Standard.Consists of Windows Server 2003 and includes Microsoft Exchange Server 2003, Microsoft Outlook 2003, Windows Share Point Services 2.0, and optionally Microsoft SQL Server 2000, ISA Server 2000 (upgrade to ISA Server 2004 in Small Business Server Premium SP1), and Microsoft Front Page 2003 in Premium edition; allows 75 client licenses.