Finally this document seems to have been released again, it disappeared quite quickly the first time it was published on Microsoft.com.

Overview
This topic illustrates how Microsoft met evolving business needs with the deployment of Microsoft Exchange Server 2007, such as reducing risks associated with spam, improving business agility, and lowering TCO. The 64-bit platform enables Microsoft IT to keep pace with ever-increasing performance expectations, raise mailbox quotas, lower storage costs, and eliminate tape backups to save additional costs.