The participants of the Windows Insider program can evaluate the updated Mail app for Windows 10, which introduced a new section Draw.
Draw section available in top menu when composing a new message. With it, users of devices on Windows 10 with touch screens, you can write emails with the stylus.
Updated email client and keyboard SwiftKey will be part of the next major update of Windows 10, codenamed Redstone 5. Its release is expected this fall.