The extensible, open source mail client.
Thunderbird is a free cross platform e-mail application that is easy to use and customize.
Mail and Calendar
Mail and Calendar is an email client by Microsoft that comes bundled inside the Windows 10
Microsoft Outlook is a paid-version of email clients by Microsoft as part of Microsoft Office with more enhanced features.
Inky is an email client.
Touchmail is an email client made by former Microsoft employees that focuses on email for touch environment.
Opera Mail is a stand alone e-mail client for Windows and OSX created by the Opera team.
Seamonkey is a Mozilla product which includes a web browser (based on Firefox), an email client (based on Thunderbird), an HTML editor, and a chat.
Yahoo! Mail is an official email app for Yahoo Mail by Yahoo! that made for Windows 10.