Mail receptacle for isolating received items in public drop boxes

A closeable mail receptacle for use inside of a drop box, includes a rectangular tub having an open top, and a top cover adapted to engage the open top and close the tub either prior to or during removal of the tub from the drop box. The top cover may include a peripheral frame adapted to engage the open top. The rectangular tub may be a standard mail flat tub and further include a non-permeable liner located within the common mail flat tub. The rectangular tub may include a peripheral flange extending horizontally outwardly from around the open top.