U+1F4ED · emoji since 2014
The open mailbox with its flag down means the mail has been collected and the box is empty. It marks an emptied postbox.
It is the icon for all clear, the open box with nothing left to pick up.
In texting, 📭️ does not carry a widely used hidden or slang meaning, so you can usually take it at face value. People send it just as it looks, to add a little visual touch or set the mood of a message. Only a handful of emoji have a separate texting code, and 📭️ is not really one of them.
Its official Unicode name is the Open Mailbox with Lowered Flag emoji. In everyday chat most people just call it the open mailbox with lowered flag emoji or describe what it shows. Copy and paste it from the button at the top of this page.
The 📭️ leads off a short phrase, and the rest of the words are written in cipher, every letter disguised as another emoji. Tap decipher to reveal the whole line.
Or make your own cipher in the translator.