"Please clarify something for me"

That is how the last email I received from a parent started. "Please clarify something for me" No "Dear Mrs. C" or "Hey You" or "To Whom it may concern" just started off into some rant about their kid or something. I hate not being addressed formally in emails. You wouldn't just walk up to someone you never met and start talking to them without introducing yourself would you? No. You would say "Hello, my name is blah blah blah" I get countless emails from parents that start this way. I just can't believe how basic manners have gone out the window! It's just so rude. I swear I could write a book on this.