Package size is a real problem at our mail facility. Like others, the opening inside is slightly larger than the outside opening. When a box just barely fits into the inside opening, it is nearly impossible to get it out from the outside. Several times we have had to assist my mom getting a package out. One time we had to actually cut the box open to remove the contents and then remove what was left of the box. One time I was out of the area and she called because she couldn't get a box out, so I told her to push it back inside because you can't relock the door to the parcel boxes.
I, too, thought they were supposed to deliver large parcels, but it doesn't apparently apply if they can jam it into the opening at the facility.