Remember those “Hello, my name is” sticky name badges? I hereby copyright “Hello, my pronoun is” and trademark its design.
The correct response to this at the git-go is to say that your preferred gender pronoun is “the general” or “General sir”, or “your highness”.
To the email, I don’t have enough eveidence to be sure it is real. Not that I doubt that that doesn’t happen. I’d sue. I’d sue for the same reason a soldier got off the boat at Omaha beach on D-day. To risk my comfort to preserve the nation.
I will use their preferred pronoun if they tattoo it on their forehead.