What do different drop slots do in the USPS office?

According to USPS regulations, the customer has to ensure that the mailbox is accessible to the postal carrier to facilitate mail delivery The

A mailbox with a lock must have a slot that is large enough to accommodate the customer's normal daily mail volume The USPS neither opens a locked box nor

usps mail slot The opening must be at least 1 12″ x 7″ · The bottom of the slot must be at least 30″ above floor · Horizontal slots must have a flap hinged at the top

slot bonus new member 200 However, the USPS has established minimum size requirements for mail compartments: at least 12 inches wide, 3 inches high, and 15 inches deep Parcel