Why can't I use school email to complete Request Verification？

When I have finished uploading the predictions of test data, the website asks me to complete Request Verification. But school email (like XXX@mail.xxx.edu.cn) cannot be used. I wonder why this happens and what format email address is valid?

This seems to be a grand-challenge related question. Maybe you can directly contact them? We do not require any special authentation on our part.