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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You must have a Chinese name for official use during your stay in Taiwan (the name will be used on your student ID card), and your Chinese name must remain consistent.

在台就学期间，您必须有一个固定使用之正式中文姓名（该中文姓名将印于学生证上以供身份查验之用）。

youdao

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。

youdao

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

He called for anyone caught "disseminating inappropriate material" to lose their jobs automatically, and suggested special advisers should not be allowed to use official resources for party political purposes.

BBC: Slur MP condemns No 10 'cesspit'