When can you send Wonder mail on pokemon mystery dungeon???
If you are referring to when can you send Wonder Mail to other people through the Wireless capabilities that the Nintendo DS has, then you are able to send Wonder Mails between two Pokemon Mystery Dungeon games regardless of where you are in the game. All that is required is that you have already started a saved game file and that is pretty much the only requirement that there is to sending Wonder Mails between Mystery Dungeon games.