I've recently had a student email about ten times regarding material completely independent of class. In fact, I don't even teach the student in one of my own classes. They just happen to know I like the topics they're interested in. I've been pretty direct in poking holes in their thinking and pointing out what I consider to be errors or lapses in understanding.
At the same time, I couldn't be more impressed by the intellectual charge they bring to the conversations and the genuine, obvious passion displayed for testing out beliefs to see how they hold up. In order to not focus solely on breaking down their beliefs and understandings, I wrote them the email below. I feel it's probably good for any student to read.
Teachers aren't all knowing and we rarely know much about what's important to the students themselves. They deserve to know that and be reminded as frequently as possible. We have to learn things just like them and that requires chasing down and tackling new knowledge and understanding actively and vigorously. Waiting for it in class is a non-starter. It may never come.