What will be a hardware consideration as well as your most important initial planning criteria is Exchange 2007’s updated server roles. Microsoft has expanded the number of Exchange server roles available to five, and that will most likely expand the number of physical Exchange servers you’ll be running. Your meat is the Mailbox server role, but a close second in importance is the CAS (Client Access Server), which manages all the proxied client connections, including Outlook Web Access, something you most certainly want (see below).

There are also two transport roles, one internal and one external. On the outside, it’s the Edge Transport server, which is not so much a router as a DMZ-safe filtering instance. A good move, but SMBs might do better to forego the DMZ-based filtering strategy and instead look to an externally hosted solution such as Microsoft’s own Forefront line or something from a competitor such as MessageLabs. Internally, your transport role is the Hub Transport server, basically an e-mail router for large, distributed enterprise deployments. Sub-1,000 user installations need not apply. 

The last server role is that of Unified Messaging. This one routes all the required data between CAS and Mailbox roles and external communications platforms including IP PBX systems and, yes, Office Communications Server 2007. Microsoft has made the actual user configuration of OCS/Exchange surprisingly straightforward, but you’ll need a Unified Messaging server running and it needs to be updated with Windows Server 2003 SP1.

Postdeployment, administrators will be working with the new face of Exchange management, Exchange 2007's ESM (Exchange System Manager). ESM's tree-style view is quite different from the 2003 manager. Once you get the hang of it, ESM is more efficient than the previous generation, but getting the hang of it is not a trivial exercise. ESM is also different under the hood. This version has been built entirely on the Exchange Management Shell, which is an extension of the Windows PowerShell scripting environment. The upside is that folks willing to dig into EMS will be able to write their own scripts to automate tasks. The downside is that Microsoft has made every facet of Exchange management functional within the command-line EMS environment, but not quite every facet functions within ESM. Parts of Exchange Server 2007 SP1 are supposed to address this inequality and make both views equal in terms of management muscle (here again, see "Exchange Server 2007 Service Pack 1 packs plenty").

Another weakness of the new management scheme is that Microsoft has placed everything inside Exchange itself. Exchange 2003 and earlier versions had MMC (Microsoft Management Console) snap-ins one could deploy to take care of frequent management tasks (including user creation and account management) from a central console outside of Exchange. That’s gone. To manage that stuff going forward, you’ll be using MMC’s Active Directory snap-ins and then clicking back to ESM to finish the job. Not our favorite admin model, and we hope Microsoft figures out a way to keep those often-used functions in a single console somewhere.