Meaning of lái xìn:
lái xìn
来信
Noun
incoming letter
Wǒ hěn gāoxìng shōudào le nǐ de láixìn.
我很高兴收到了你的来信。
I am very happy to receive your incoming letter.
Verb
to send us a letter
Wǒmen qídài shōudào nǐ de láixìn.
我们期待收到你的来信。
We look forward to receiving your letter.