Hotmail delivers aliases to help you manage and secure your email account

[Corrine]

One more great addition to Hotmail!  This is a step beyond the already available Hotmail feature to add a plus sign ('+') and a descriptive word to the first part of your email address.

Starting today, you can add up to five aliases per year to your Hotmail account, up to fifteen aliases in total, all designed to make it a lot easier to organize different types of email and personas in one Hotmail inbox without having to give out your primary email address if you don't want to. 

From http://windowsteamblog.com/windows_live/b/windowslive/archive/2011/02/03/hotmail-delivers-aliases-to-help-you-manage-and-secure-your-email-account.aspx