We have the problem every business dreams of having.   Clients are bringing by work faster than we can keep up with.  At first they were just inserting it into our mailbox and we would find it the when we checked the box.  Then an issue arose about items without postage being placed there so we had to create a new way.  We searched for commercial mailboxes and discovered that had a 2 inch by 20 inch slot and we knew that would handle anything that we would received.  We purchased the large size and mounted it securely right outside our office door so it would be convenient to everyone.