Maintaining inbox zero is like a game of whack-a-mole. For every email deleted, organized, or responded to, another one pops up in its place. However, that only happens if your email is always open. By just opening up email and responding to it at set times during the day, you can process messages in batches and be much more productive. When you finish, close your email, and get to work.
I don’t have to check email as much these days as I have in the past, but I check it anyway if it’s open. I check it even when there’s nothing new in there. Ideally, there could be a notification when the inbox has 10 new items, or email could launch automatically two hours from the time I closed it.