1.
A letter, especially a formal one.
书信书信，尤指正式信件
2.
confidential information, files, letters
机密情报、 文件、 信件.
3.
acknowledge receipt of a letter, an order, etc
签收信件、 订单等
4.
interchange gifts [letters]
交换礼物 [信件]
5.
A second - class letter is slower than a first - class .
二等信件比一等信件慢点。
6.
written in the form of or carried on by letters or correspondence.
以书信或者信件的形式写的，写在书信或者信件上面的。
7.
Letters are delivered every day.
信件是每天递送的。
8.
An instantaneous reply to my letter.
对我的信件的即刻答复
9.
He stuffed the papers down into the box.
他硬把信件塞入箱子里。
10.
I am tired of sorting out mails every day.
我讨厌每天把信件分类。
11.
sift through the piles of correspondence
仔细检查成堆的信件
12.
a backlog of work, unanswered letters
积压的工作，待覆信件
13.
The postman delivered the letters promptly.
邮递员投递信件很迅速。
14.
letters for the manager to sign
需要经理签字的信件
15.
Tie up these letters and see that they don't come loose.
捆好这些信件，别散了。
16.
old correspondence still unattended to
仍未答覆的旧信件.
17.
registration of letters, parcels, trunks, etc
信件、 包裹、 衣箱等的挂号
18.
ELSIE (Electronic Letter Sorting and Indicator Equipment)
电子信件拣分显示装置