In the basement of MACUSA memos write themselves, then fold into origami rats. They use the glass tubes to scurry to the offices above. On occasion they will start to fight and tear each other apart, leaving the intended recipient memo-less.
Is there a system in place for the memos that never get sent because the rats tear each other apart? Is a replacement memo automatically magically made? Or do MACUSA employees frequently walk around oblivious?