A student email address only provides unlimited storage if your institution has a subscription for it. We added a note to the storage settings to let users know it might be worth adding their institutional email in case their institution already had a subscription or purchased one in the future. Unfortunately this has led to a lot of confusion, so we've removed the note for now.

If you've added your student email and your storage settings do not show a note that your institution provides unlimited storage for that email address, then your institution does not have an active subscription that provides you free storage. (NTNU does not)