Dead Letter mailbox
A Dead Letter mailbox is a mailbox that contains AS2 messages that might not be routed for some reason. The Dead Letter mailbox is available by default in Global Mailbox under the root mailbox as /DeadLetter. A Dead Letter mailbox cannot be deleted or renamed.
If you already have a mailbox that is called Dead Letter in your setup, you must delete or rename the mailbox before you upgrade to v6.0.1 or later. Otherwise, the existing Dead Letter mailbox is overwritten with the new Dead Letter mailbox and your existing messages are lost.
You can create submailboxes under the Dead Letter mailbox. You can also move messages from the Dead Letter mailbox or delete them. While moving messages to a target mailbox, if the target mailbox has an event rule that matches the messages, events are generated and the files are routed.
An administrator can check the messages in the Dead Letter mailbox periodically for the messages that are not routed correctly and resolve them.