[Exim] freezing on failure

Has anyone have a suggestion for a method of freezing messages that get
a 5xx error. I have a problem that requires that when the message
fails it is frozen, and a message is sent to the sender about the
failure. This is for a document delivery issue, under the law and our
contracts, we are unable to make copies, but we can stop the delivery
process.. but to save time when there is an error in repeat the
process, especially for an email address error. It would be great to
actually just treat it as it has been frozen, after the failure.

Jason
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Jason Robertson
Now at the Nation Research Council.