They’re making it possible to integrate different email addresses into your Hotmail account, without changing your email addresses. Basically, this means that you can register and validate your existing email address from any email client (like Gmail, Yahoo! Mail, etc.) and read and use it within the Hotmail interface. Kind of like Microsoft Outlook, only web-hosted.
You’ll be able to use all Hotmail features (and they’ve rolled out plenty of new ones recently). If you want to find out how to do, read their instructions here
The reason why hotmail is making this changes according to Dick Craddock, Group Program Manager at Hotmail, is because they understand that most of us already have an email address and that users don’t always want to inconvenience themselves by changing their existing address. “You already have at least one email address and you probably don’t need another.
You may also use your existing address for things other than just email, such as signing in to online shopping sites, which makes changing even more challenging. Also, you might have an address that you really like, but a similar name might not be available on another email service. So we looked for a way to make it easier for people to give Hotmail a trial run.” Apparently it will take a few days for this feature to be available internationally.