Wouldn’t it be great if you could have one email address for all your friends, one email address you use to sign up for potentially spammy services and sites you don’t really want to get in touch with you, another for business and then one more for all your gamer friends?

That’s exactly the idea behind the new aliases feature announced this afternoon for Microsoft Hotmail’s 350 million users.

The new feature allows users to add up to five new aliases a year, up to a maximum of 15.  But why would you want to add aliases? Dharmesh Mehta, director of Windows Live at Microsoft, explains:

The email address a person uses is a big part of their online identity. The average person maintains three different email addresses in order to organize different types of email, maintain different personas, or keep junk mail away from a primary email address. So there are many good reasons that people want multiple email addresses, but maintaining multiple accounts, with different user names and passwords that require you to check multiple inboxes, is inefficient.

Mehta offers the example of searching for a car. You may have to sign up for several sites, but once you’ve found the car, you now have all this email still coming. With aliases, you can simply turn off the alias and – voilà ! – the emails stop.

As you can see in the screenshot, when you set up the alias, you are also given the chance to direct all that alias’s email to a specific directory. This makes it simple to keep email separated so you can easily ignore pay attention to what’s important.