Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!
Evolution - Apps/Evolution - GNOME Wiki!
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Postbox - The Power Email App for busy professionals, like you.
Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
Avanti! Mail Client - Avanti! Mail Client is one of the best email accounts management program for the Windows operating systems.