dead letter

音标发音

Take the dead-letter drop, where an item can be left inconspicuously and securely for someone else to pick up.
把秘密情报投放点选择在东西留在那里而不易被发现却可以让别人安全的取走的地方。
Messages can be put on the dead-letter queue by queue managers, message channel agents (MCAs), and applications.
消息可由队列管理器、消息通道、消息通道代理程序（MCA）和应用程序放到死信队列上。
In more robust environments, set up a dead-letter handler as a trigger so that the dead messages are automatically re-tried without intervention.
在要求最可靠的环境中，将死信处理程序设置为触发器，以便自动重试死消息而无需人工介入。

The library shelves are a sequence of dead-letter boxes, ideal hiding places for illegal missives between friends (or even lovers), breaching the strict segregation lines between male and female prisoners.
ECONOMIST: Unlocking the books in a prison library
This deal was of a piece with other actions taken by Moscow and Beijing to water-down the UN sanctions resolution to the point where it was virtually a dead-letter even before it was adopted.
CENTERFORSECURITYPOLICY: Securing America's energy needs
Is -- are the separate developments that are expected -- the North Korean nuclear freeze, the shipment of food -- however you care to characterize it -- is the hope for a breakthrough with North Korea a dead letter because of the satellite launch?
WHITEHOUSE: Press Briefing

(MAIL) a letter that cannot be delivered to the address written on it and cannot be returned to the person who sent it
(LAW/AGREEMENT) a law or agreement that is no longer effective

If you say that a law or agreement is a dead letter, you mean that it still exists but people ignore it.