Profile: Mail Boxes G B specializes in supplying banks of post boxes and letter boxes to the construction industry. Our post box/letter box & mailbox is a galvanized steel horizontal post box with security lock and anti-theft lip to aperture. Our letter box comes with 2 keys. Fire protective single mailbox is a galvanized steel vertical post box with security lock and anti-theft lip to aperture. It detects and extinguishes a fire in less than 15 seconds. A discreet fire extinguisher activates automatically when the fire raises the internal temperature of the post box.