This is the Postfix program at host mx01.263xmail.com.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The Postfix program

<hr@o-r.com.cn>: host 127.0.0.1[127.0.0.1] said: 550 hr@o-r.com.cn:mailbox
limit exceeded (in reply to end of DATA command)

楼上翻译得差不多了，不过可能你看不明白吧。

其实意思很简单，hr@o-r.com.cn 这个邮箱满了（或者是你的附件太大，对方有邮箱大小控制），打个电话过去让对方删些邮件吧，如果是有邮箱大小控制，就要对方网管修改了。