Designed to replace the current Mail and Calendar apps, the new Outlook can only be removed after it's been installed.

Microsoft will automatically install its new Outlook client on Windows 10 PCs with next month’s Patch Tuesday update.

Microsoft will force install the new Outlook email client on Windows 10 systems starting with next month's security update.

Microsoft decided to force install the new Outlook on Windows 10 starting with the new updates of the OS. You can quickly uninstall it after.

The good news is that the February update which brings the new Outlook doesn't strip out the old version of the app, so you can still use that.