Snailbox - Schedule your email at specific times and recover the time you're losing to your inbox.
Noisli - Noisli is a fantastic background noise and color generator for working and relaxing. Online soothing ambient sounds like White noise, Rain and Coffee Shop.
Inbox When Ready - Protect your focus... hide your Gmail inbox by default
Noizio - Feeling that the noise of the big city is too much for you to bear?
Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.
Moodly - Get a better sense of focus and relaxation by listening to ambient nature sounds.