noun
mailbox (for receiving mail); letter box
Refers to a private mailbox where delivered mail is received, such as at a home or office.
郵便箱をのぞいたら、手紙が届いていた。
When I checked the mailbox, a letter had arrived.
noun
Refers to a public collection box where outgoing mail is deposited, often red in Japan.
角の郵便箱に手紙を出しに行く。
I'm going to drop this letter in the mailbox on the corner.