We have a user who used Import, instead of 'Open Data File', to import a large number of mails from a pst file which he exported, instead of archived, years ago. As we can see, there are now many duplicate mail items in his Outlook. Is there any way to de-duplicate the mail items in Outlook?
https://www.ablebits.com/office-addins-blog/2013/10/10/remove-duplicate-emails-outlook/
Will.