We use email for more than just messaging people. These other things could be reminders for things such as paying bills, or even relying on them to act as tasks to accomplish. Unfortunately, outside of filing messages in a to do label or folder or marking them as unread, it's difficult to stay on top of them. Especially since we all get so much email (spam messages aside) that it gets to be a task just even reviewing messages. Announcing a solution: Boomerang.