OSX Mail App Using Tons of Memory and CPU?

I’ve been using a mac for a while now and I recently decided to dump Entourage and go to using the native Mail.app.  I noticed a problem though.. within minutes of starting up it would consume several hundred megs of ram and have frequent CPU spikes of 80 to 100%.  If Mail was left open, memory usage would climb above 2 gig with continued CPU spikes.  After much digging I finally found the problem and fixed it.