This mod adds a "Pack in Crate" menu item to every item in the game (with a few exceptions) that can't normally be placed in an inventory. By selecting this menu item, you will search the tray for an empty packing box and move this item to your inventory.
This is a simple English dialect modification to replace instances of 'mail' (American English) with 'post' (British English), as well as changing 'mailbox' to 'postbox', and 'mail carrier' with 'postal operative' (the official gender-neutral equivalent of 'postman' in the UK).