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Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Geary - Geary is an email application built for GNOME 3.
MyEmail - MyEmail is an online service that works as a free email service system making its clients able to check their emails from any part of the world.
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.