Corporate users who migrate to Exchange 2007 will face mandatory infrastructure changes that, while advancing security and management, could add complexity and costs to their networks.

The major changes beyond the 64-bit-only platform include a new role-based architecture that has the potential to require users to roll out up to five types of Exchange servers to support functions such as remote client access, transport/routing, mailboxes and unified messaging. The current versions of Exchange give users two deployment options, front-end servers and back-end servers.

Users also will face new clustering limitations and will have to eliminate all Exchange 5.5 servers from their environments. In addition, they will not be able to do in-place upgrades between Exchange 2000/2003 and Exchange 2007. And Exchange no longer will have its own site topology but will run on top of Active Directory topology.

In addition, Microsoft has yet to release detailed migration and best practices guidelines to users. The first public beta of Exchange 2007 is due by the end of July.

“More complex, yes,” says Peter Exstrop, a network consultant for WM-Data in Sweden. “Before, all the roles were on the same server, but now you will have more servers.” While Exstrop acknowledges that nearly all the Exchange 2007 roles can be deployed on one server, for larger deployments that will not be a viable option.

“But I look forward to splitting the server roles,” he says. “Security is better, you don’t have to have a complete Exchange server in your DMZ to receive mail.” With earlier versions of Exchange, those servers in the DMZ were viewed as a security risk.

Another major area of change will be clustering. Users will only be able to cluster servers deployed in the mailbox role. And edge servers, which can supply e-mail hygiene services such as anti-virus/spam protection, will be required to run on a dedicated server and with Active Directory Application Mode.

“We had our routing [service] on a cluster and now it needs to go somewhere else, and that means more servers,” says Christopher Wenzel, applications analyst for the law firm of Katten Muchin and Rosemann. Wenzel, who has clusters running in four of his five Exchange sites around the United States, noted that best practice guidance from Microsoft for Exchange 2003 was to cluster servers. “In the past, the idea was server consolidation, but not anymore. Now it is scaling out again. My footprint increases in that I need more servers and more money for licensing [Exchange and Windows].”