Keeping your sex a secret

I had to write a letter to one of my union mukka-muks. I have no idea whether or not I have spelled the word correctly and this time--oddly enough--I don't give a rat's a**! The mukka-muk's name was "Jerry" and I wrote my salutation, "Dear Mr. F-------,"
In response, Jerry stated that she is a female. "I guess it's misleading and I'm sorry about that."
I was momentarily infuriated because in my opinion when you are in a position of authority you shouldn't do stupid things like using a nickname. The only time I would cut slack to over something like that is those poor folks whose parents gave them initials for a first name. "Jerry", I later found out, is NOT her Xtian name.
Just a little rant of the moment... of which I seem to have so many these days