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

Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!

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

Mailbird - Mailbird is the best email client for Windows 7, 8 and 10

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.

Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.