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.

the mail slot in the red boxes has NOTHING to do with Aust Post regulation sizes.

if you purchased the 10mm CD mailer, just check if your dummies fit in that box, when taped close.

ask at the nearest LARGE post office for one of their mail gauges