yóujiàn zhǔtí zhǐ xiě zīliào shí shōujiàn rén hěn nán zhīdào yào xiān kàn nǎ yī fēng

邮件主题只写“资料”时，收件人很难知道要先看哪一封。

When the email subject only says "Documents", it's hard for the recipient to know which one to read first.