It encodes the data in such a way that the mail transport agent is unlikely to modify the resulting octets.

这种对数据的编码方式使邮件传输代理不可能修改结果八位元。

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For example, if you're packaging a mail user agent or mail transport agent, there are some specific considerations that apply.

例如，如果您正在对一个邮件用户代理程序或邮件传输代理程序进行打包，那么有些特定的考虑事项适用于这种情形。

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Acting as an agent of international and domestic air transport of express mail, package and goods.

代办国际、国内快件及货物的航空运输业务。

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