题目

Undelivered Mail Returned to
给国外的朋友发邮件,然后收到一个纯英文的系统恢复,内容如下：
This is the mail system at host bjsd-tm-app7.localdomain.
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 mail system
:host mx4.hotmail.com[65.55.33.119] said:550 SC-001
(COL0-MC5-F8) Unfortunately,messages from 211.100.40.146 weren't sent.
Please contact your Internet service provider since part of their network
is on our block list.You can also refer your provider to
FROM command)

提问时间：2021-03-27

答案

就是说你发的邮件,没有发出去,没有达到对方的服务器!
可能是网络问题,也可能是对方的服务器设置了对国内的邮箱拒收!