Rated 5 out of 5 stars
The program works correctly and has helped me eliminate duplicates, especially after mail has been downloaded onto two computers and then is merged.
It did not eliminate duplicates in the merged Sent folder, which is by design. I reported it as a bug and within an hour Eyal told me to set a parameter (removedupes.allowed_special_folders) to have the Sent folder also scanned.
He deserves 5 stars plus 1 more for responsiveness.