State your name, disclose any relevant bits (I am a journalist; I am a government official; I may publish your response; etc.), and ask your question. You might

State your name, disclose any relevant bits (I am a journalist; I am a government official; I may publish your response; etc.), and ask your question. You might have a signature that gives more disclosure, like a phone number. Providing context is, as a rule of thumb, a bad idea. It takes time to read it, and that's the exact opposite of the point of a one-liner. If it's necessary for answering the question, then chances are the question is too broad or poorly targeted: your recipient ought to already have the necessary context. That's what makes them useful for asking your question. That said, it's just a guideline, which means break it when you feel like breaking it. Everyone is going to have a different threshold for what seems rude, what seems worth answering, and so on; you kinda have to go with hit or miss. Only this past week, I actually got a response back from an author I emailed over a month ago. I had stopped expecting a response two days after I sent it off and moved on, so it was a very pleasant surprise.