"item is still being delivered"

[Kurobon]

When you try to access mail other than from a mail-npc, it has a message like "item will be delivered soon" or something.. However, it should say something like "receive mail from the treasure keeper".

 

This confused me greatly when I started using the game, because I thought it would arrive eventually, but it never did. I had to visit the treasure keeper to get it. (without paying for instant delivery)