Very short question regarding proper salutation

[Alucard7]

Hello.

This question might appear unnecessary/obvious/ridiculous, but I really need to know. I am a medical student writing an e-mail to another medical student who lives in the UK. I have not met this student nor spoken to him, I know both his first and last name and he is probably around the same age as me (23-25).
My question is: How do I start the letter? (e.g. for someone called John Smith)
Dear Mr. Smith
Dear Dr. Smith
Dear John
Hello
Hi
???
I am required to contact many students in the same way and don't want to make a bad impression, because they may have an important role in evaluating me for a scholarship.
Thank you in advance for any help...

[billmcd]

I would use "Mr." unless you know that he is a doctor. In that case use "Dr.".

[Alucard7]

Thank you for answering!
I will use Mr. Ms. just to be on the safe side...