Determining Server Limits

There is no explicit limit on the number of users you can configure to reside on a single Microsoft Exchange Server computer. However, there can be practical limitations dictated by the time it takes to back up a very large server database. Practical limits not directly related to server performance can prove to be the limiting factor on the number of users a server can support.

There is a 16-GB limitation on the size of the public and private information store databases (32 GB total), but this limitation will be removed in the next version of Microsoft Exchange Server. Presently, this limitation can become a factor on larger servers hosting many users, depending on the following factors:

The amount of server storage used by each client.
Whether client quota limitations are used and their values.
The degree to which single-instancing of messages and attachments increases the logical storage capacity of the server.
The extent to which personal folders are used, and to a lesser extent, the number of rules, views, and finders that are defined by users on the server.