The default view of Unibox with a list of all people you exchanged emails with ordered by last message is a great match for most people, expecially for low and medium email volume. But once you reach a certain amount of emails each day that you need to get done with, the default view might not be the best option.
A concept that many people have switched to is called "Inbox zero". It means that you only keep emails in your inbox that still need some action. Once you are done them you archive the message. After you worked off all emails your inbox is empty, i.e. "zero".