[Exim] How to copy delivery confirmation replies to two mail…

Hello,

How can I get exim to copy receipt messages from a source to two mailboxes.
The original recipient gets the mail but an auditing system needs to get a
copy of it as well to log for say efficiency reasons (mail turn-around time)

I've seen the "unseen" option for the router in FAQ Q9809, however, i dont
seem to find one for a particular mailbox.
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Thank-you for your time.

John Ward