Polymail - Native email app for email productivity.

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

Morning Mail - A new way to manage your mail. Tinder for email.

Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.

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

Strikethru - Strikethru is a kind of to-do list notebook for managing work lists and staying updated with the important tasks.