If you use GMail, consider giving their Inbox client a try. If you find you use your email Inbox like a To-do list (leave it in Inbox till it's handled), Inbox is perfect for you. It DOES take some getting used to, but having used it for personal and business accounts for many months now – I can't imagine switching back. The best part though? You always CAN switch back to the normal GMail interface (GMail is
http://mail.google.com and Inbox is
http://inbox.google.com). In fact, you can switch between them as often as you like. Inbox is definitely worth a try, especially on mobile. Be sure to read the tutorials and hints to get started!