Once upon a time, Microsoft made some standalone applications for Windows machines under the Windows Live Essentials moniker. A few of these apps were quite popular, including the Windows Live Writer blogging app that has since gone open-source, Movie Maker that was good enough for quickly editing video and uploading to YouTube, and Windows Live Mail. The packaged topped out at version 2012, and has since been superseded by Microsoft's various other apps for Windows 10 (or, in some cases, by nothing at all).
Anyone using Windows Live Mail 2012 alongside an Outlook.com email address will want to start reconsidering your choice of a new email client. Simply put, Microsoft's update to Outlook.com utilizes protocols that Windows Live Mail 2012 doesn't support, and so if you're on Windows 10 then you should start getting used to the Mail & Calendar app sooner rather than later.
To provide you an email experience with enhanced performance, security and reliability, the new Outlook.com has been built upon our latest Office 365 infrastructure. Because the Windows Live Mail 2012 email application doesn’t support the protocols used by this new infrastructure, you will not be able to send or receive Outlook.com email from Windows Live Mail 2012 after your account is upgraded. This means the time has come for you to upgrade to a new email application.
The company provides this response to Windows 7 users who haven't upgraded yet to Windows 10 (even though Microsoft has confirmed that the Windows 10 upgrade will indeed no longer be free after July 29, 2016):
Q. What if I am using Windows 7 and do not wish to upgrade to use the Mail app?
A. If you do not wish to upgrade, you can access your account via a web browser or you can take advantage of a free one-year subscription for Office 365 Personal and use Outlook 2016 to connect to your account. Details on how to redeem this offer are included in the email communications from the Outlook.com team. This Office 365 subscription includes the Outlook 2016 email application as well as other productivity applications such as Word, PowerPoint and Excel. It works on Windows 7, Windows 8/8.1 and Windows 10.
There you have it, Windows Live Mail 2012 fans. Your days of using the app to access your Outlook.com account are numbered and Microsoft really wants you to move on to something else. Let us know in the comments if this applies to you, and what you plan to do about it.