Dear Professor [name],
My name is [Preferred name], and I will be attending your course [blank] on [days] at [time] this [term]. I am transgender and have not yet legally changed my name. On your roster is my legal name, [Legal name]. I would greatly appreciate it if you refer to me as [Preferred name] and use [pronouns] when referring to me. Thank you for your understanding, and I look forward to starting your course next week.
You don’t owe people the person you used to be. You don’t have to talk to people who are speaking to the old you. If they want to drag old you out, and you’ve already left that person behind, they don’t get to talk to you. When you’ve gone from weakness to strength, you don’t owe a show of your former self to someone who just can’t wrap their head around your change.