I have a couple users that have problems with the Outbox folder in their mailbox. We are running Exchange 2010 with Outlook 2007 clients. The problem we are seeing from a couple users is that messages are randomly piling up in the Outbox, but they are not visible. If I attach their mailbox to my profile I can see messages in the Outbox and can clear them out. The crazy thing about it is that the users say that the messages are being received by the destination even though the messages never make it to the Sent Items folder. It doesn't happen to all of their messages, only some of them. Also, there is nothing unique about the messages such as internal, external, small, large, etc. It is completely random. We have tried deleting the profile on the local machine without luck. Anyone have an idea?