Besides bug fixes, the new icons are the major new component of preview Build 19569.1000. SEE: 20 pro tips to make Windows 10 work the way you want (free PDF) In a Medium post, Christina Koehn ...

The Mail and Calendar icons are now rolling out to public release builds of Windows 10. Previously, they were available only to Windows Insiders in the Fast and Release Preview rings.

Microsoft is starting to refresh its Windows 10 icons for apps that are built into the operating system. It’s part of a bigger focus on more colorful design under the Fluent Design system.

Microsoft released new icons for its Office suite reflecting its move to the cloud in 2019, and it's been rolling out updated icons for Windows 10's core apps (such as Calendar and Mail) since then.