CRM Preview features are new features that are made available in advance of being supported. They are usually made available in CRM Online.
More details available here.
Related Posts
Update Rollups for Microsoft Dynamics CRM 4
28 March 2008 28 May 2022
Problem configuring Outlook Client when host headers are used
28 March 2008 28 May 2022
Installing CRM 4.0 in Windows Server 2008
28 March 2008 28 May 2022