寄信給客戶，無法送出被退信，而該客戶可正常寄給我們。
被退信內容

This is the Postfix program at host ms.liontools.com.tw.

I'm sorry to have to inform you that your message could not be 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

<joanne-chen@mmm.com>: host 3m.com.inbound15.mxlogic.net[208.65.145.12] said:
554 Denied [CS] (Mode: normal) (in reply to end of DATA command)

<speng3@mmm.com>: host 3m.com.inbound15.mxlogic.net[208.65.145.12] said: 554
Denied [CS] (Mode: normal) (in reply to end of DATA command)

上面訊息是代表那邊出問題了？該如何解決呢？