This is a quick tutorial on in-game notes/lettersStep 1: Put a piece of paper in a chest.
Step 2: Get the "modify item strings" filter for mcedit if you don't already have it.
Step 3: select the chest and open the filter.
Step 4: For name put Note or the name of the letter/note.
Step 5: In lore, write down what the note says.
Step 6: roll over it in minecraft and it should be able to be read.
Optional: if you want to, make a custom trade for the letter for delivering or something like that.