Define the user base that you want to test (for example, Lightweight IMAP).
If necessary, adjust individual parameters to best match your usage profile.
Define the hardware that will be tested.
Run the load simulator and measure the maximum number of concurrent connections on the tested hardware with the user base.
Publish your results and compare those results with production deployments.
Repeat this process using different user bases and hardware until you get the response time that is within an acceptable range for your organization under peak load conditions.
Contact Sun Client Services for recommended load simulators and support.