Double postage estimates good time, a letter sent in advance to your friends, but not stamps, nor do they want their addresses to write a letter (or else turn back to you).

• 双倍邮资估算好时间，提前给你的朋友寄一封信，但不要贴邮票，也不要把自己的发信地址写上(不然就会退给你的)。