Sometimes Hotmail (Microsoft's mail provider - Outlook, MSN, Live, etc.) claims your account doesn't exist when someone tries to send mail. You should just be able to re-verify if that occurs.
Well it did work, but then it messed up again...it kinda keeps happening about every 10 minutes now.
But it isn't a huge effort to change e-mail and change it back. I just wanted to let you know something is going on.