They had a mail service, although it was for official use only.

建立了邮政系统，虽然只供官方使用。

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The consular bag may contain only official correspondence and documents or articles intended for official use and must be sealed and bear visible external marks of its character.

领事邮袋以装载来往公文、公务文件及公务用品为限，应予加封并附有可资识别的外部标记。

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Some nations use English as their official language, performing the function of administration; in others it is used as an international language for business, commerce and industry.

一些国家用英语作为官方语言，并用它履行行政职能；而在其他国家，它被用作商业、贸易和工业的国际通用语言。

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They had a mail service, although it was for official use only.

建立了邮政系统，虽然只供官方使用。

耶鲁公开课 - 新约课程节选

Mazzanti expects the Army will anoint two mobile operating systems for official use.

CNN: U.S. Army may soon equip troops with smartphones

You can print out the receipt for your records and use it as the official donation receipt for tax purposes.

FORBES: Charitable Giving

Use the official website for the Wales Coast Path, which links to regional websites with relevant details.

BBC: Walking the new Wales coastal path