最近在服务器A上装了imail,但只能外发不能收，能收到imail内部用户的信。
在sohu上发信，sohu退信内容：
This is the Postfix program at host websmtp1.mail.sohu.com.
I'm sorry to have to inform you that the message returned
below could not be delivered to one or more destinations.
For further assistance, please send mail to
If you do so, please include this problem report. You can
delete your own text from the message returned below.
The Postfix program
: host mail.longh.net[222.89.202.250] said: 550 5.7.1
Unable to relay for user@mail.longh.net
另说明：服务器A本身没有设置dns，dns设置是在isp服务商51web那进行的,然后指向服务器A的服务器地址。
