Over the past couple of days a few mails have floated through my Inbox asking for advice on capacity and performance planning for Ex2003. It can be quite a challenge to make sure that your Exchange Infrastructure is up to the job and planning is key to a successful installation.
I posted previously on an article written by two Exchange MCS guys here in the UK disussing how to use JetStress and Loadsim but you may also want to make sure that you plan for any "What-If's" well you can using the Capacity Planner
"Microsoft System Center Capacity Planner 2006 helps size and plan deployments of Microsoft Exchange Server 2003 and Microsoft Operations Manager (MOM) 2005 by providing you with the tools and guidance to deploy efficiently while planning for the future by allowing for "what-if" analyses"
I assume, that when our own internal perf testing hascompleted that this tool will be updated to accomodate Ex2007. I will let you know as and when.