sender
noun [ C ] uk/ˈsen.dər/ us/ˈsen.dɚ/
发送者；寄件人
a person who sends something
Postage stamps were introduced in Britain in 1840 as a way of showing that the sender had paid for the letter to be delivered. 1840年，英国开始使用邮票，以表明寄信人已付邮资。
The letter came back with "return to sender - not known at this address" written on it. 信被退了回来，上面写着“退还寄信人——此地址查无此人。”