我想寄封挂号信。

I'd like to send a letter by registered mall.

这是您的挂号信，请您签收。

This is your registered letter. Please sign for it.

您收到挂号信的时候要签收。

You have to sign for it when you receive a certified mail.

凡属正式通知以挂号信邮寄一式二份。

Formal notice sent by registered mail shall be in duplicate.

我妈给我发了一封挂号信，我想她有什么重要的事情要说。

My mother has sent me a registered letter, I guess she has something important to tell me.