As some have rather obscure requirements (never fish/give away your seeds/fish etc), I'm wondering how many are ther ein total?
In my 108 stars playthrough with Eresh recruited, I got 211 so far. I compared the list with this FAQ on gamefaqs and saw that I was missing 23 (most of them Euram related)http://www.gamefaqs.com/ps2/929668-suik ... faqs/42195
I also know that if Belcoot dies in a War Battle, Marina and Hazuki each leave a letter in your box.
So thatÄs 211+23+2= 235 letters in total? There are a lot of characters who only send you one or two letters, so there might be more.
EDIT: Ok, got the answer via tumblr - 288. Wow.