Ans - You can delete duplicate emails from Opera Mail using the Aryson Opera Mail Backup Tool. This application provides a feature to remove duplicates from your Opera mail. Here is a step-by-step instruction to remove them: 1. Firstly, Download and install the Aryson Opera Mail Backup Tool.  2. Preview all folders from the tree structure list. 3. Select the folders you want to convert to PDF, then click Next.  4. Choose the PDF format from the Save/Backup/Migrate As menu. 5. Then, Choose the Include duplicate emails feature and others. 6. At last, click on the Convert button.