I always send an email to my professors about a week before the semester starts that says this:
SUBJECT: Preferred Name
Body:
Dear [PROFESSOR’S PREFIX AND LAST NAME],
My name is [YOUR FIRST AND LAST NAME], and I will be attending your course [COURSE TITLE] on [DAYS OF CLASS] at [TIME OF CLASS] this semester. I am transgender and have not yet legally changed my name. On your roster is my name is [LEGAL NAME]. I would greatly appreciate it if you refer to me as [PREFERRED NAME] and use [PREFERRED PRONOUNS] when referring to me. Thank you for your understanding, and I look forward to starting your course this week.
Sincerely,
[PREFERRED FULL NAME]Also, look into seeing if your school has a preferred name policy! My school just implemented one last August! It still has some loose bolts so I email my professor’s still anyway but it can be helpful on school IDs and such!
As a prof, this is both overkill and perfect – very polite and very thorough.
I only say ‘overkill’ because I get a lot of email in August and September and would be happy with something that got to the point a little faster:
Dear Professor [name],
I’m in your [course number or title] class, [section number if applicable] this semester. My name on official documents is [legal name], but I would greatly appreciate it if you would use [preferred name] and [preferred pronouns].
Thanks for your understanding, [etc.]
I don’t need to know why, unless someone is comfortable disclosing. I just need to respect it.
(I’ve even had “hey, my name on the list is [name] but I go by [name] and [pronouns] instead. cool?” … But I teach in a very informal department, and while I was fine with it, I wouldn’t actually recommend that course of action as a first contact. XD )