3 sentences

1. 国家的邮政系统正在进行改革。

   guó​jiā de yóu​zhèng xì​tǒng zhèng​zài jìn​xíng gǎi​gé.

   The national postal system is undergoing reform.

   Source: Dong Chinese Dictionary

2. 在那个年代，铁路和邮政等事业都由国家专营。

   zài nà​gè nián​dài, tiě​lù hé yóu​zhèng děng shì​yè dōu yóu guó​jiā zhuān​yíng.

   In those days, industries like railways and postal services were state-operated monopolies.

   Source: Dong Chinese Dictionary

3. 请在信封上写清楚邮政编码。

   qǐng zài xìn​fēng shàng xiě qīng​chu yóu​zhèng biān​mǎ.

   Please write the postal code clearly on the envelope.

   Source: Dong Chinese Dictionary