Exchange Deployment Options Whitepaper
The purpose of this paper is to help you choose how to deploy Microsoft Exchange: as Exchange Server 2010 on-premises, Exchange Online with Microsoft Office 365 in the cloud, or using both in a temporary or permanent hybrid scenario.
Download this whitepaper at https://www.microsoft.com/download/en/details.aspx?id=18206
Read my favorites blogs:
Designing a backup less Exchange 2010 Architecture
Microsoft Exchange 2010 CAS Array – Steps and Recommendations
Appear Offline in Microsoft Office Communicator Server 2007