Seeking zero inbox (archive emails), but still wanting to keep track of actionable emails on a duedate ? You could move your email into the "next" folder, but what to do when it is due on a specific date ?
In GMail, now that we have tasks, we can attach a duedate to emails by creating a task related to the email. Then we can archive the email and forget about it until the date comes: we see the task in our calendar and a link to the related email.
Open the email, click on "more actions", and click "add to tasks". Then set the due date. Then you can archive the email.