The Outlook.com integration also includes the voice calls and instant messaging capabilities for which Skype is famous.
Skype for Outlook.com is integrated with the online version of Microsoft’s People app and it automatically imports your Skype contacts so they’ll be available to you on Outlook.com. And once you've downloaded the plugin, then proceed to link your Skype account to Microsoft account to take advantage of the inbox calling functionality.
Simply by hovering your mouse over a contact's profile picture or the blank contact icon at the top of the message pane, and then selecting the phone or video calling icon and your Skype call will start. Alternatively, click on the messaging icon on the far right side of the Outlook.com interface.