主题: 求助:客户发邮件被iredmail服务器退回

退信信息如下,请问是什么原因引起的?谢谢
The attached message had PERMANENT fatal delivery errors!

After one or more unsuccessful delivery attempts the attached message has
been removed from the mail queue on this server.  The number and frequency
of delivery attempts are determined by local configuration parameters.

YOUR MESSAGE WAS NOT DELIVERED TO ONE OR MORE RECIPIENTS!

Failed address:
user@domain.com

回复: 求助:客户发邮件被iredmail服务器退回

对方服务器出问题了吧