Kontact - KMail!

Microsoft Outlook, part of the Microsoft Office Suite (not to be confused with Microsoft Outlook Express), is a personal information manager that lets you manage your e-mail, calendar, contacts, and tasks.

eM Client is a full featured email client with a modern and easy to use interface. - offers calendar, tasks, contacts and even chat.- fully optimized to run smoothly on Windows XP, Vista, 7, 8 and 10.- supports all major services including Gmail, Exchange, iCloud, and Outlook.com.- easily imports your data from most of the other e-mail clients. This includes Microsoft Outlook, Outlook Express, Windows Mail, Windows Live Mail, Thunderbird, The Bat and more.- fully supports touch devices like touch-enabled laptops, tablets and hybrid devices. Use your email client easily in a modern way.- finds any email, contact or attachment in seconds with eM Client's super-fast search. »

Apple Mail changes the way you interact with your email every day.

Postbox is an email application that helps you organize your work life and get stuff done.

Geary is a lightweight email program designed around conversations and built for the GNOME desktop.

Claws Mail is an email client (and news reader), based on GTK+, featuring

EssentialPIM lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.

Sylpheed is a simple, lightweight but featureful, and easy-to-use e-mail client (mailer, MUA).

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

Open365 is an Open Source, self-hosted file sync and cloud apps platform including a full LibreOffice Online. You can also access your email, calendar and contacts using KDE Kontact. Everything is accessible from a simple webpage using any HTML5 browser.

Polymail is the modern email client, redesigned.