What items do you keep in letters?

[BungoTheElf]

I usually keep my tools in there! Once in a while if I need to keep furniture or something in there I do~

 

[Byngo]

Tools and some of my other knick-knacks like toy hammer, pinwheels, stuff like that~

 

[Selky]

Mostly tools or items I just bought that I don't want villagers bugging me for.
As for letters at the post office I have saved. I've mostly used them to store seasonal
items like the creepy set and spooky set.