In the email, it clearly states not to directly reply to that email address. They list an email address within the email to reply to. You may have to reply to it twice before they receive it. I had to reply to it two times before I finally got en email confirming the time slot I chose for my interview. Hope that helps. And definitely be prompt with your response, as it also says that if they don't get a reply within 24 hours, they will assume you aren't interested. I agree they could stand to do better with this process, a phone call would be better than an email, but that's how they operate since they have a LOT of candidtates trying to get on board with them.