Todoist - Todoist is a to-do list that helps you get organized, at work and in life.

Polymail - Native email app for email productivity.

Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.

Airmail for iOS - One of the best Mac email clients, now on iPhone

EssentialPIM - EssentialPIM is a free Personal Information Manager that keeps up with the times and lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.

Airmail - Airmail is a lightweight and lightning fast mail client for Mac.