|There is no direct facility with Poco to do this now but there are a couple of possibilities I can think of.
Austin wrote a script for Poco 2 that tagged duplicate messages within a mailbox.
I can't find it on the Poco website but it might be possible to modify that script to do this.
It depends on how the script was run.
I'm very much suspecting this isn't possible with the script as it probably was searching within the one mailbox.
Rachel wrote a script that iterates through Poco's mailbox index files and pulls information for marked messages and puts that into the QuickGuide.
This concept could be used to find duplicate messages (but it would be VERY slow - it would be faster if you just wanted to find any message anywhere that was a duplicate of the current message or, perhaps, duplicates of any message in the current mailbox).
This is also only possible with Poco 3, Poco 2 did not store the message id header in the mailbox and even with Poco 3 there is a problem, the index files are currently not committed to disk immediately upon update and there is no way I know of to force this via a script (except perhaps via the CompressMailbox command).
There is a way to find duplicates of the current message across mailboxes.
View the full headers for the message and copy the message-id header to the clipboard.
Open Poco's search function and search for the message-id across all mailboxes (you may have to compress all the mailboxes first).
To find the location of the messages that are found view the short headers in the Search mailbox.
You can use the "Found in" link to go to the duplicate message in the mailbox.