camail

例句：

1. 1.I received a letter from my sister last week.
   我上周收到了姐姐的一封信。
2. 2.The postcard from her arrived yesterday.
   她的明信片昨天到了。
3. 3. He sent me a letter to let me know he was safe.
   他给我寄了一封信，让我知道他很安全。