I agree that if you send the E-mail to the office, they might accept it. But for the future, it is your responsibility to follow the official deadline and --- if uncertain --- to be conservative (i.e. you should always submit a copy by the earliest deadline). Then, if you still have time, you can always make improvements and resubmit. But the rule is that, at university, you are responsible. So you need to make sure that you are always on the safe side.