Is "Hey John" too informal in an email?
Here's the hierarchy of salutations from most formal to least formal: Dear, Good Morning/Hello, Hi, Hey, Wassup??, Dude!!!!! Many 20-somethings are afraid to use “Dear John” in emails because they think the next line should read: “I’ve loved you from afar.” You shouldn’t be afraid to start with “Dear John”; he probably doesn’t love you either. “Dear John” is fine in emails; it’s a formal greeting. Use “Dear John” when you don’t know someone well, and John hasn’t yet set the tone for what kind of relationship you have. Take cues from him. If John gets back to you with “Alice,” or “Hi, Alice,” follow his lead. Just watch out for “Hey-ing” someone until you know for sure you’re on a “Hey” basis.