Microsoft's recently released Exchange 2007 package is huge, literally. The reviewer's guide comprises 26,000 words, and the list of new features is 28 pages long. In this Clear Choice Test, we opted not to test every bit of code, but instead to dive deep in several critical areas important to large-scale deployments.

Overall, we found Exchange 2007's management and availability extensions are improved dramatically, and new architectural maneuvers have beefed up security, especially in the areas of compliance and e-mail policy management.

However, when we enabled Microsoft’s new antispam software on our Exchange 2007 deployment, we found that  it requires more engineering effort to compete with established vendors in that market.

Exchange 2007 is sized for the largest enterprises, because it requires 64-bit hardware. That signals that the product will need substantial hardware, software, network bandwidth and operations resources. We didn't run strenuous, repeatable benchmarks on Exchange 2007 for this features-based test.

With Exchange 2007, Microsoft has solved one of the messaging platform's long-standing reliability issues by allowing for true database replication to independent storage subsystems. We used Exchange 2007's Cluster Continuous Replication service to build a cluster of two mailbox servers, each with independent disk storage. We turned off the cluster's active node and watched it continue to operate without a hitch.

The active/passive model consumes twice as many resources, depending on how the disk storage is replicated, but the cost of additional hardware could be low compared with the cost of losing an enterprise e-mail system.