The Old Letter is a key item that appears in Paper Mario: The Thousand-Year Door.
The Old Letter is given to Mario by Podley after explaining why Admiral Bobbery refuses to go back out to sea. It turns out to be a letter from his deceased wife, Scarlette, who explains her last words. This letter must be given to Bobbery who reads it out loud. In the letter, Scarlette tell Bobbery that she doesn't blame him for her death and he should continue doing what he loves. Bobbery manages to get over his bitterness over the seas and decides to head for Keelhaul Key with Mario and the others.