MBOX DUPLICATE REMOVER
When I got some MBOX files from my friend and opened them in Thunderbird, there a lot of duplicate mailboxes so to fix duplicates, I use MBOX Duplicate Remover Tool that has a power to remove MBOX duplicates in bulk. It simply fix all mailbox duplicates in one round and without any damage to any file. Therefore, I recommend you this application. You can download the demo version right now.
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