10 sentences

1. 情况紧急，请速回信。

   qíng​kuàng jǐn​jí, qǐng sù huí​xìn.

   The situation is urgent; please reply immediately.

   Source: Dong Chinese Dictionary

2. 请记得给朋友回信。

   qǐng jì​de gěi péng​you huí​xìn.

   Please remember to write back to your friend.

   Source: Dong Chinese Dictionary

3. 她没有给他回信。

   tā méi​yǒu gěi tā huí​xìn.

   She didn't write back to him.

   Source: Tatoeba

4. 至今我还没收到他的回信。

   zhì jīn wǒ hái méi shōu​dào tā de huí​xìn.

   I still haven't received a reply from him.

   Source: Dong Chinese Dictionary

5. 他整天盼着能收到家里的回信。

   tā zhěng​tiān pàn zhe néng shōu​dào jiā​lǐ de huí​xìn.

   He looks forward all day to receiving a reply from home.

   Source: Dong Chinese Dictionary

6. 我等你回信。

   wǒ děng nǐ huí​xìn.

   I'll be waiting for your response.

   Source: OpenSubtitles

7. 你回信了吗？

   nǐ huí​xìn le ma?

   Did you write a reply?

   Source: OpenSubtitles

8. 他回信了吗？

   tā huí​xìn le ma?

   Did he reply?

   Source: OpenSubtitles

9. 他到现在还没回信，莫非是没收到我的邮件？

   tā dào xiàn​zài hái méi huí​xìn, mò​fēi shì méi shōu​dào wǒ de yóu​jiàn?

   He hasn't replied yet; could it be that he didn't receive my email?

   Source: Dong Chinese Dictionary

10. 他至今还没有回信，由此可见他并不想参加这个活动。

    tā zhì​jīn hái méi​yǒu huí​xìn, yóu​cǐ​kě​jiàn tā bìng bù xiǎng cān​jiā zhè​ge huó​dòng.

    He hasn't replied yet, which shows he doesn't want to participate in the event.

    Source: Dong Chinese Dictionary