When we write to people we don’t know, we have to consider what to call them. Should we use their first name? First and last name? What about their title?

If you are writing to someone who works for you, is younger than you, or is otherwise someone you are equal to or have authority over, then you may use the person’s first name. This is called downward communication.

Typically, if you are writing to someone who is in a position of authority relative to you—a potential employer, someone older, a teacher, or a government official—using their first name is not appropriate. We think of this as upward communication, where we are writing to people with a position deserving of particular respect relative to ourselves. To show that respect, we address them first by their title and last name, only moving to the first name once instructed.

Our system of titles is very basic. Mr. Last for men or Ms. Last for women. There are more titles for women denoting marital status, but these are generally not used professionally unless instructed by the woman to call her by that title. If a woman is married and wants to use Mrs. Last, she will let you know.

A student recently told me about a woman he had contacted as Ms. X who threw a little tantrum at not being addressed by her married title of Mrs. X. He said that her response made him question whether he should use Ms. or not. I find her reaction confounding. Ms. is the appropriate title for a professional woman because it does not denote marital status. If a woman would like her martial status to be clear in her title, Mrs., it is the responsibility of that woman to kindly indicate that. An angry reaction to someone following protocol makes it more difficult for all of us to establish and follow a basic set of rules for addressing unknown women in professional settings.

Mr. and Ms. are the standard. If the recipient prefers another title, it is his or her responsibility to indicate that. For example, I have earned my PhD, so my title is Dr.; I am happy every time I have the opportunity to gently correct an innocent writer addressing me as Ms.