4B+ Vertical Mailbox - Recessed Mounted - 4 Doors

4 slot mailbox   Dan 4 slot

This 4C versatile™ mailbox from US Mail Supply holds four oversized tenant slots, perfect for an apartment, office building, or campus dormitory Easily mounted

Column Mailboxes with mail slot Shop Mailbox And Beyond for residential mailboxes of all types for the lowest price guaranteed  I think the introductions to each mechanism on MSDN answers this: Mailslots: A mailslot is a mechanism for one-way interprocess

book of sun slot Ideal for an entry, hall, mud room or office Feature 3 Complements a variety of design styles Feature 4 Grey Buy Now $ Free Worldwide Shipping Linon Industrial Metal Four Slot Mailbox Shop