Outlook.com allows you to make use of several types of Keyboard shortcuts mode (Yahoo!, Google or the default Outlook one). This feature is quite useful for people migrating from a different email service to Outlook.com, as they can have the hotkeys arranged in the same way it was on their onld messaging service.
To change or even turn off keyboard shortcuts:
From your Outlook.com home-screen, click on Settings > More Mail settings.
Go to Customizing Outlook > Keyboard shortcuts.
Select the mode of your choice and validate with the Save button.