It badly affects the productivity of the business. Duplicate emails enlarge the size of the Outlook data files uselessly.
Duplicate items will enlarge the size of the Exchange/Office 365 mailbox.
So here we will focus on how to delete duplicate emails in Outlook 2013. Once the data is moved completely, you cannot eliminate the duplicate items so easily. When you transfer items in MS Outlook, and the duplicate detection option is not enabled or turned on.