The Nuts and Bolts article Outlook Synchronization in Microsoft Dynamics CRM 4.0, which is available for download from the Microsoft Download Center:
Outlook synchronization enables Outlook users to view Dynamics CRM information, including contacts, tasks, phone calls, letters, faxes, appointments, and e-mails, within the Outlook interface. This document describes the client synchronization process that is associated with Update Rollup 7 for Microsoft Dynamics CRM 4.0 or later (for on-premise deployments) and with Microsoft Dynamics CRM Online November 2009 Service Update or later (for online deployments).