I see 2 folders under PM - Tracking vs Outbox. I sent a couple of IM's but I only see 1 of them in Oubox - the others are in Tracking. What is the difference between the 2 folders?

To the best of my understanding, under Tracking you can see all the PMs you send, and you can see if they have been read by the recipient. Outbox only stores those outgoing PMs for which you have checked the box to do so when you sent it.