Inbox, Outbox
This is an inbox installed at the door of the house or on the side of the road. The small red flag is put down, indicating that there is no mail waiting to be received in the box.
It should be noted that blue or gray mailboxes are displayed on most platforms, and a few platforms depict inboxes in red.
The emoticon can be used not only to express the meaning of e-mail and postal delivery, but also to indicate that there is no pending mail or that the sent mail has been retrieved.
