Exchange 2K load testing

Hi there, I'm designing an exchange 2k platform and am looking for a way to send several test messages at the same time so that I can test the load that the pipe will handle. It's for a gov't contract and it's a small pipe we are working with to go between domains. Does anyone know of any tools out there that will allow me to set this up so that I can just tell it how many messages to send and how often so I can see when the pipe dies on me?

Thanks in advance for your help.

Jer