Why do I need to verify my Microsoft account / email address?

We require that you verify your email address when you use it to create a Microsoft account or when you add it to your existing Microsoft account. That way, we can verify that the email address doesn't belong to someone else. To sign in to Microsoft products and services, you have to verify your email address.

When you sign up or add an email address to your account, you automatically receive an email request to verify your address. To verify, just follow the link in the message.

If you try to sign in using an email address that hasn't been verified, you're asked again to verify it.

If you need a new verification link for an email address you added to your Microsoft account, request that a new link be sent to you in email.

To request verification email

1. Go to the Microsoft account overview webpage, and then sign in with your Microsoft account.

2. Click Verify next to the email address, and then click Send me verification email.

Source: http://windows.microsoft.com/en-us/windows-live/account-verify-id-email-address