Gmail's unique selling point is the control it gives you over your inbox, with the option to star, label, and archive your mail as you see fit without the need to ever permanently delete regular messages. Google is taking a similar approach to your outbox from today, giving you the ability to star and label your own messages before you hit the Send button. Why would you want to do that? The primary use case is for messages that you know you'll want to follow up on — now you can designate labels and categories for outgoing mail, or simply star the messages worth keeping an eye on. The labels are only seen by you, of course, so feel free to organize them as you want. Just try not to get too stressed at the mounting list of messages you haven't gotten a reply to yet.