Few days ago, Microsoft enabled the IMAP protocol for Outlook.com accounts. This is definitely good news for all users of alternative email clients, such as Mozilla Thunderbird. Access to a mailbox via the IMAP protocol provides several benefits over POP3, which was the only option available for Outlook.com/Hotmail users previously, if they did not use Microsoft's Live Mail application. With IMAP, you are able to access all the folders on your server. Also, IMAP saves the "read/unread" state for all your messages as well as the complete list of your messages which is accessible through all instances of your email clients, even across multiple devices.
So, here are the instructions on how to configure IMAP in the Thunderbird email application.