If your Thunderbird still show duplicates after cleaning MBOX file. Simply you can try a specialized tool like SameTools MBOX Duplicate Remover. The software quickly scans MBOX files detects duplicates by sender, subject, date, and message content, and deletes only repeated emails while keeping the originals. It is compatible with all Windows versions including 11, 10, 8.1, 8, and 7. The tool can process multiple MBOX folders at once, works smoothly with large mailboxes, and features an intuitive interface for both beginners and advanced users. A free trial lets you preview results before final removal.
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