Microsoft has released the Exchange Load Generator 2010 (LoadGen).
LoadGen allows you to test how a server running Exchange 2010/2007 responds to e-mail loads. To simulate the delivery of these messaging requests, you run LoadGen tests on client computers. These tests send multiple messaging requests to the Exchange server, thereby causing a mail load. LoadGen is a useful tool for administrators who are sizing servers and validating a deployment plan. Specifically, LoadGen helps you determine if each of your servers can handle the load to which they are intended to carry. Another use for LoadGen is to help validate the overall solution.
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