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…
Yeah! I’ve used it all of last year and it went over really well. Everyone said they’ll do it and nearly all of them kept up on their word, and the ones who misgendered me still did so out of negligence to remember rather than spite. But they all used the correct name at least ^_^;
The year before that I went up to the professors in person and told them and it went off well I guess but by that point they already had my given name and pronouns in their heads so it was a bit more difficult for them to adjust, but it wasn’t anything /too/ bad. Id say if you have the option to, then use the email approach ahead of time so they have time to adjust.