Really useful when you're testing your authentication system so that you can easily sign up with email addresses that don't already exist in your system. Particularly useful if you're automatically sending a welcome email and want to verify that it works.
@libovness A trick I use o test authentication on new projects is to append a variable to my email address when registering - e.g. andy+test@leadin.com.
Unless you've coded it, your system won't recognize the duplicate, but you'll still receive the emails from your app.
I've only tested this hack in GMail/Google Apps though, so maybe other mail providers don't automatically forward.
Antimatter Studios
Email Wars
Tettra