https://www.theverge.com/2018/6/26/17505490/microsoft-windows-10-mail-app-stylus-support

Microsoft first got serious about digital inking in Windows 10 a year after the operating shipped. The software maker added Windows Ink in the aptly named Anniversary Update to improve stylus support for devices with a pen. Windows Ink was a good first step, and Microsoft has been gradually improving its inking across Windows 10 ever since. Microsoft is now finally bringing stylus support to the Mail app in Windows 10.

Windows Insiders can test the latest Mail app update, and it includes a new draw tab in the ribbon interface when you compose a new email. You can now write an entire email with a stylus if you like, and it’s something that has been strangely absent from Windows 10 for three years now. There are plenty of pen options and colors with this new feature, and it should ship in time for Microsoft’s next major Windows 10 update, currently codenamed Redstone 5. Microsoft is expected to make this update available in September, and the company is getting close to finalizing its feature set.