Send the letter registered return receipt requested mail and keep your proof of receipt.

注册送信件和邮件不断要求归还收据证明你收据。

youdao

Note this Return Receipt only acknowledges that the message was displayed on the recipient's machine.

注意“返回收据”只是用于确认消息已经在收件人的机器上显示过。

youdao

Note: This Return Receipt only acknowledges that the message was displayed on the recipient's computer.

注意：这封回复函只是确认(你发送)的信息已经显示在接受者(收件人)的计算机上。

youdao

The USPS has long provided senders with a return receipt option.

FORBES: My Software Isn't Creepy

In the present case, Allen County sent both of the tax sale notices at issue by certified mail, return receipt requested, to the address listed in the mortgage document and to another local address.

FORBES: Wells Fargo Ignores Mail Loses Security Interests

To improve your chances of getting full credit, provide a sales slip or gift receipt, return the item in new condition, unopened, and with all packaging material.

FORBES: Returning A Gift? What You Need To Know About This Year's Return Policies