I need to send a case to the French Ministry of Justice for personal issues, so this is pretty much an official and important mail. I don't know who will read this mail so I can't begin the letter with something like,
Dear Mr./Mrs/Ms. Robinson,
Anyways, I wouldn't know how to use the two expressions above should the addressee person be of a different gender.
To my knowledge, there's no established rule to handle this situation in French.
What's the etiquette for beginning a formal letter (in English) when you don't know who will read it? I don't want to offend the person who will read it should they be of a different gender than those addressed by the "Sir" and "Madam" words. I'm most interested in French etiquette but I'm aware there are not so many French-speaking people around so, I'm interested in any way to express it in English that I can translate later on.