A drop-box mechanism or system is disposed adjacent to an article conveyor and atop a flat mail storage tub and comprises a platen movable between first and second chambers at which the open top of the storage tub is respectively uncovered and covered. When the platen uncovers the storage tub, deflecting fingers move downwardly so as to cover the platen tracks and the space defined between the bottom of the drop-box mechanism and the open top of the storage tub so as to prevent flat mail articles from becoming jammed within the tracks or from being inadvertently discharged through the space defined between the bottom of the drop-box mechanism and the open top of the storage tub. In this manner, the predetermined conveyed order of articles is preserved so as to facilitate sequence address delivery of the articles to recipients.