If an email is not urgent until later, most people tend to leave it in the Inbox. This causes you to look at it (i.e. spend time and focus on) over and over. A much better way is to move it out of your Inbox. SaneBox offers another tool for this - Snooze Folders. Move an email into one of them, and the email will pop back in your Inbox at a predetermined time - when it becomes actionable.