I've been using Microsoft Outlook for quite some time, & duplicate emails were slowing down my mailbox. Then I found GainTools Outlook Duplicate Remover, which solved my problem quite easily.

Key Features

• Fast scan & removal of duplicate emails
• PST file support
• Emails, contacts, task, & attachments cleanup
• Secure removal with data protection
• Improving Outlook performance

If your Outlook is slowing down due to duplicate items, this tool can prove to be very useful.