Francesco Cesco,
Simple method now compare message id if available. If not uses the advanced method.
Advanced method compare recipients, body, subject, message date, attachments names, attachments size, etc. You can see them if run
Duplicate Outlook Items Report utility with Show diagnostic information option enabled.
Also Removing duplicates using our Utility is NOT an one-way operation. You can revert it.
Please see our
video how you can do this.