A lot of people here get their milk delivered to their doorstep — or used to anyway. You can still see the boxes — some wooden, some plastic — hanging here and there around town.
The box on the left with the yellow characters just visible around the symbol of the star — 雪牛乳 or Snow Brand Milk — has been smartly co-opted to serve as a mailbox. The owner has written ゆうびんうけ (mailbox) in black marker across the front in hiragana — perhaps to do it in Kanji was too much of a bother (郵便受け).
On the right is a nice example of an old wooden box (sorry it's a little out of focus) for Meiji Milk. Notice the telephone number on the side of the box in Kanji which helps give away its age.