Windows Live Admin Center (changed from Windows Live Custom Domains in November 2007) is a service provided by Windows Live. It enables users with domain names to change their domain MX record (Mail Server) so that they can enjoy the full features of Windows Live Hotmail on their personalized domain.
Email accounts provided by Admin Center are Windows Live IDs and you can use them to sign into MSN Messenger and Windows Live Messenger and all other Windows Live ID enabled services.
One Windows Live ID can be set as the administrator and using that ID new accounts can be created, and old ones can be deleted or edited on that domain. The administrator may also choose to allow anyone to create his or her own account in the domain via a link on the domain’s web site. Administrators can choose from a web-based or Windows-based application to manage all aspects of their domain accounts.
Users with Admin Center accounts can check their emails using Windows Live Hotmail, Windows Live Mail, and Outlook.
This tutorial will show you step by step How to Configure your own domain with Windows Live Admin Center.
You will see a page similar to this below. You will work with “MX Server” under Mail Setup category.