Bad: No formal address at all.
Worse: Messing up titles (Miss, Madame, Lady, Herrin,…)
Worst: Addressing the completely wrong person!

If you really feel the need to send the exactly same request via copy and paste to a plurality of ladies at least have the brains and decency to make sure to put in the right name in the first line.
If you cannot manage that don’t be pissy about the lady if she is not as accomodating as you would wish she would be. There is a ton of timewasting idiots out there trampling on the nerves of your prefered lady. It’s your job to show her that you are not one of them – and it’s not that difficult at all. Just a little effort and respect and she will, too 🙂

By the way: That goes for private and professional Dommes alike 🙂