So i  wanted to test what i could fit into the post box slot,   I forgot to get the gauge but i did grab a cd mailer box.  It was a 10 mm box  and it didnt fit into the box.  Am i being a dumb blonde here lol.  Is the gauge thing in the post office wider then the mail slot.    I know i can open the shute and throw the package in, but i was under the impression i guess it also had to fit into the mail slot on the red post box.