Whether you choose the Standard Edition or the Enterprise Edition of Exchange Server 2003 depends on your organization's size and the Exchange features you require. Typically, the number of users supported becomes the key reason for selecting one edition over the other; both editions have the same components, the same administration and management tools, and the same servers. Let's take a look at each of the editions.
Exchange Server 2003 Standard
Exchange Server 2003 Standard Edition incorporates the same server functionality as the Enterprise Edition: web access, mobile access, reliability, and security. The Standard Edition is primarily targeted for small- to medium-sized organizations that do not require the feature-rich enterprise-level messaging functionality required in larger organizations. For example, the server may be used as an email server for a small organization, a front-end server in a larger organization, or a bridgehead server for an Exchange organization.
As previously mentioned, Exchange 2003 Standard Edition supports a single storage group with two databases (one mailbox store and one public folder store) with an individual database size of 16GB. The database size is a limiting factor in the number of users that can be supported. Clustering support and X.400 support are also missing from this edition. Be sure to analyze your particular environment before choosing the Standard Edition for your organization.
Exchange Server 2003 Enterprise
The Enterprise Edition of Exchange Server 2003 is targeted at large and worldwide organizations that need more than a 16GB messaging database. With support for up to four storage groups, with each storage group containing up to five databases, a single Exchange 2003 Server can support up to 20 individual information stores. Unlike the Exchange Server 2003 Standard Edition, the information stores in Enterprise Edition are limited only by an organization's hardware budget and the hardware being used, with a theoretical limit of 16TB (terabytes) of storage.
Enterprise Edition also supports clustering capabilities, which allow for maximum system availability and fault toleranceusually a top priority for large organizations with a large number of mailboxes and mail storage.
In addition, the Enterprise Edition includes an X.400 connector, which is not supported in the Standard Edition of Exchange.
Table 1.1 compares the Standard and Enterprise Editions of Exchange Server 2003.