Along with a new release of Windows 10 for Windows Insiders, build 10166 today, Microsoft also released an updated SDK Preview to go along with it. The company has promised to try to keep the SDK updated current to the latest build, so that developers can try out the latest changes in the soon to be released operating system.
In addition to bug fixes and improvements, SDK 10166 contains changes to Windows.ApplicationModel.Email, with “additional getter properties added”.
Microsoft recommends uninstalling the build 10158 SDK and emulators if you have them installed before downloading and installing the latest SDK.
If you don’t have Visual Studio installed, you can try out the new SDK on the free Visual Studio Community 2015 edition. Visual Studio 2015 is set to come out of beta on July 20th.