Howdy-do!
I would like to suggest the idea that you are purrsented with a postcard-like image based on where the letter was sent from! Fur example, if someone mailed you a letter in Ul'dah and you opened it at your house in Lavender Beds, you'd briefly see a pop-up image (think pretty much everything at the Gold Saucer) and then the letter would be opened up.
"Greetings from Ul'dah!" *image of the Steps of Nald*
"Wish you were here!" *image of Costa Del Sol*
I think it would be easy to implement while adding a lot of purrsonality and life to getting letters. Yes yes.
Thank you fur reading! (* ' - ')/