A destination unreachable error PDU was received.
收到了一个目的地不可达的PD U协议数据单元错误。
Or an destination unreachable message, when there is no route available such as when a line goes down.
或者，当没有可以使用的路径时，比如某条线路被关闭了，ICMP会发出无法送达目的地的信息。
The destination port is unreachable.
无法连线到目的连接埠。
This message was undeliverable due to the following reason: Your message could not be delivered because the destination server was unreachable within the allowed queue period.
以下理由导致您的信件无法寄达：由于无法在允许的伫列周期之内与目标伺服器取得连线，导致这封邮件无法寄达。
This message was undeliverable due to the following reason: Your message could not be delivered because the destination server was unreachable within the allowed queue period.
以下理由导致您的信件无法寄达：由于无法在允许的伫列周期之内与目标伺服器取得连线，导致这封邮件无法寄达。
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