Your must have a clear functional unsubscribe facility built into the message you send.

在发出的邮件中必须预设一个有效的“退出”功能。

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This facility must allow the recipient to unsubscribe by sending a message back to the sender, using the same method used by the sender without incurring any costs.

该功能可以让收件人以发件人同样的方法，在不产生任何费用的情况下，用回件方式退出收件人名单。

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