Microsoft Exchange Hosted Services Overview

Microsoft Exchange Hosted Services is composed of four distinct services that help organizations protect themselves from e-mail-borne malware, satisfy retention requirements for compliance, encrypt data to preserve confidentiality, and preserve access to e-mail during and after emergency situations. The services are deployed over the Internet, which helps minimize up-front capital investment, free up IT resources to focus on value-producing initiatives, and mitigate messaging risks before they reach the corporate firewall.

Here is the overview of MS Exchange Hosting Service.