This confidential letter must be given to him in person. 这封密函一定要亲自交到他得手中。
My letter is, of course, strictly private and confidential. 当然，我的信纯属私人信件，务须保密。
Dummy can be magisterial and deferent epistolary confidential letter, even if is captured to also ask not clear exact details. 哑巴可为长官传送书信密件，即便被俘也问不清底细。