Yep, the letters were fairly simple and could be used successfully in one of 2 ways.
Open your own letter on the correct day (as per the number):
Mafia player - gets basic information about a random character
Non-mafia player - gets basic information about a mafia character
Open someone else's letter on the correct day (as per the number):
All players - get detailed information about the character the letter originated from, and their powers (but not alignment)
Anything else - poof! Letter bursts into flames. I think about 75% of them were wasted in this way, which was actually a few more than I expected.
The reasons why I introduced the letters was twofold. Firstly, I wanted players to have something to kick-start the game and actually have some form of info to work with from day #1. The letters went from day #1 - #5 to continue this and provide a bit of a spicy variable and get you all thinking. Second reason - I just wanted to mess with your heads.
So, I'm keen to hear what you all thought of this particular mechanic? I may use something similar (like a "clue drop") again at some point...