Leading Hands are big fans of Gmail. Recently the email provider launched Priority Inbox which I have been trying and liking. Google says it works like this, “Gmail's servers look at several types of information to identify the email that's important to you, including who you email and chat with most, how often you email with these people, and which keywords appear frequently in the emails you read.”
You virtually will see two bars on your screen, one for “Important and Unread” and then an “Everything Else” section. If you leave Priority Inbox, you can return to it by clicking the link next to Inbox on the side navigation of Gmail.
If you have a Gmail account, try it out. If you don't have a Gmail account get one.