Try this : I think it's quite good. I "used to use it" until I switch over to Gmail. If I remember it correctly, it worked quite well for me.
MAPILab - Duplicate Email Remover - Outlook plugin for deleting duplicate emails and posts
"Duplicate Email Remover
Current version: 2.14.2
Duplicate Email Remover is a powerful and flexible Microsoft Outlook plugin intended for the search and processing of duplicated mail messages in Microsoft Outlook folders.
This Outlook plugin processes both email messages and posts in mail-type Microsoft Outlook folders. To remove contacts, notes, tasks, journal and calendar items, please try another our Outlook tool — Duplicates Remover for Outlook plugin.
Please, pay your attention that Duplicate Email Remover can be used with Microsoft Office Outlook only. If you use Outlook Express, look at another MAPILab software - Remove Duplicates from Outlook Express plugin.
You can use this Outlook plugin to find mail message copies both in a single folder and in different folders. A duplicate message found can be:
# marked with flag Red flag
# copied to any folder you choose
# moved to any folder you choose
Duplicate Email Remover Screenshot So, you can easily test this Outlook plugin and preview messages you may need to delete.
The Priority system within the plugin is used to search for duplicates across several folders. Using the priority system, you can specify, for example, that of the two identical messages stored in the folders "Important Letters" and "Temporary Folder", it is the message from the temporary folder that should be considered the duplicate and hence needs to be deleted (marked, moved).
Duplicate Email Remover is Outlook plugin, that is fully compatible with Microsoft "http://www.mapilab.c...k/duplicate_remover/