There is a new document available to download from the Microsoft Download Center, Exchange Hosted Archive Service Description.
Brief Description
Microsoft Exchange Hosted Archive (EHA) provides a centralized, easily accessible e-mail and IM repository to assist organizations manage retention, compliance, e-discovery, and regulatory requirements. This whitepaper describes the services and features that are included in Exchange Hosted Archive.
Overview
Microsoft Exchange Hosted Archive (EHA) is a Microsoft Online Service and provides a centralized, easily accessible and multi-functioning e-mail and IM repository to assist organizations manage increasingly complex retention, compliance, e-discovery, and regulatory requirements. This whitepaper is intended for business decision-makers and technical administrators and describes the services and features that are included in Exchange Hosted Archive.