To Forrest Bump: Thanks for your response. We are American citizens and we rented the car from Hertz. We would like to go back to Italy at some point in the future.

My confusion is that the initial letter did not say that we had to provide those details. It was as simple as faxing them the form, had it been clear in the letter that we had to send that information.

They gave an email address, can we explain the situation and at least get a reduced fine? The fine is actually around 310 euros.