>>2 is right. You need to meet other people, and find other people to like. Also, reduce exposure to him, even if you don't need to flat out ignore him.

This being said, I think you girls are forgetting one side of the equation: the guy... Is he at all interested in the other girl? In you? He also has his part to play here, you can't just distribute guys among girls ^_^

So before giving up on the guy, do make sure he's really interested on the other girl, or more importantly, if he's not interested in you. After all, you do say he's constantly e-mailing you. It would be stupid to frustrate his feelings and yours just to safeguard your friend's unrequited love.