If you are managing an enterprise running Microsoft Exchange 5.5 on Windows NT 4.0, you find yourself in an especially uncomfortable and challenging position. Not only must you cut back on IT spending and do more with less, but you are also faced with the expiration of mainstream Exchange 5.5 support (as of December 31, 2003). In addition, Microsoft has discontinued support for Windows NT4 since the end of 2004, forcing an upgrade to Microsoft Windows 2000. In short, you need to make a critical decision about your new communication platform.
You could migrate your enterprise from Microsoft Exchange 5.5 to Microsoft Exchange 2003, but this is a complicated and costly endeavor. Newer versions of Microsoft Exchange run only on Microsoft Windows Server 2000 or 2003, and require the use of Microsoft's proprietary Active Directory. Thus, if you upgrade Microsoft Exchange, you need to upgrade the operating system, and you need to migrate the Exchange 5.5. directory to Active Directory as well. In-place upgrades are not possible, so the newer versions of Microsoft Exchange must be set up on separate servers and connected to the 5.5 environment to relocate mailboxes and databases to the new boxes.
The migration is costly, partly due to Microsoft's high software costs. A July 2004 report from Ferris Research estimates that a Microsoft Exchange 5.5 to Microsoft Exchange 2003 migration costs upwards of $250 per user. [The Cost of Migrating From Exchange 5.5 to Exchange 2003, Ferris Research, July 2004]
Perhaps most importantly, even if you decide to migrate from Microsoft Exchange 5.5 to a newer version of Microsoft Exchange, your enterprise might still face many of the weaknesses and limitations inherent in the Microsoft Exchange platform. Exploring alternative solutions is a must, particularly in a difficult economic environment.