A receptacle or slot for receiving mail at a house or building; can be individual or for apartment complexes.
朝、郵便受けを見たら荷物の不在票が入っていた。
In the morning, I checked the mailbox and found a delivery notice for a package.
集合住宅の郵便受けは名前順に並んでいることが多い。
Mailboxes in apartment buildings are often arranged in name order.
新しく引っ越した家には郵便受けが玄関の横に付いていた。
The new house I moved into had a mailbox attached next to the entrance.