mail slot

When I’m in the mailroom, I check my mail slot to see what mail has arrived overnight. A “slot” is normally a small rectangular opening in something, but a “mail slot” is a small box that has a person’s name on it and holds mail for that person.

Hyphenation: brie‧ven‧bus. ... mail slot, letterbox.

Additionally, to ensure smooth mail flow through the mail slot during delivery, the USPS specifies that the interior hood for privacy must align above the bottom of the outside plate on a horizontal mail slot.