In the field of computer science, there is an open proprietary file, which is used to archive entire Outlook items like emails, contacts, calendar, tasks, etc. This Outlook storage file is named as personal storage table (widely known as PST) files, having a .pst file extension.

In a single PST file, there exist bulk emails in it. Among these emails, there may be some emails, which are duplicate i.e. one email is present multiple times. Therefore, in this blog we are going to study about Outlook Duplicates, how are these duplicates generated, and learn a manual way to remove Duplicate Outlook emails with ease.

About Outlook Duplicates

Microsoft Outlook storage file has a collection of mailbox items, which may contain a number of duplicates. These duplicates are named as Outlook Duplicates, which slow downs the speed and performance of Outlook. Outlook users must have come across multiple identical data, which are same as the original files and are stored in PST file (hence, increasing the file size).

For improving or increasing the performance of Outlook, one need to erase all the emails or other data from mailbox items that are present multiple times.

Causes of Outlook Duplicates Occurrence

There are various reasons due to which duplicates occur in Outlook and some of them are mentioned below:

  • Received Mail Multiple Times: One of the most common reason is that the sender has being mailing one email multiple time. Sometimes advertisers, different companies, etc., send one email multiple time for gaining the receiver’s attention. Therefore, such activity gives rise to email duplicates.
  • Improper Synchronization: Sometimes due to improper synchronization between the electronic devices and Outlook, multiple copies of mail gets generated. If any interruption occurs at the time of synchronization, then this will lead to Outlook duplicity.
  • Issues in Server Connectivity: Leave Messages on the Server – an option in Outlook used to keep a copy of mail on the server. However, due to some fault in the server, there may be some useless duplicate mailbox items that gets downloaded from the server when connected. Therefore, try to deactivate Leave Messages on the Server option from settings.
  • Improper Outlook Configuration: Another cause for the presence of Outlook duplicates is that the Outlook is improperly configured. Examine that a rule of Outlook i.e. move a copy to rule should be enabled only once for a particular mail because if this rule is enabled more than once, then it will lead to duplication.
  • Anti-virus Application Installation: Majority of users are unaware of the fact that the multiple copies of Outlook items are also generated due to the installation of anti-viruses applications on their machine. Therefore, to remove this issue users should disable the functioning of anti-virus while working with Outlook.

Measures To Delete Outlook Duplicates

There exist two provisions by which one can get rid of this trouble and they are described below:

Using MS Outlook For Removing Duplicates

  1. Launch MS Outlook application on your machine
  2. Click on the folder from which you want to remove duplicate.
  3. Go to the menu strip of Outlook and click on View button.


  1. From different options appearing in View menu, click either on Change View >> Single or Change View >> Preview. In this content, we are going to choose the first option.


  1. Now from the Outlook column heading, right-click on it and then click on Field Choosers option.


  1. From the field choosers window, click on the Scroll-down button and select All Mail Fields option.


  1. Now perform drag down operation on the current window and select Modified option from it.


  1. Remember that the multiple copies should have a unique date as of original item sets. Now sort the items by click on Modified heading.
  2. Hold the Shift key and then select the duplicate data.
  3. After selecting the items or data, click on Delete button from your keyboard for removing Outlook duplicates.

Limitations Of Above Mentioned Solution

  • Lengthy Removal Procedure: The above discussed procedure is quite lengthy and tedious. The procedure is useless, if users are not having the full knowledge of Outlook.
  • Irrelevant for Bulk Outlook Items: When talking about bulk items that are present in multiple copies, it becomes complex procedure to delete such data using Outlook and consumes a lot of time.
  • Limited to Particular Outlook Version: The procedure is useless for the users who are using Outlook 2007 and the earlier versions. This approach is valid only for Outlook 2010, 2013, and 2016 users.

Using Third-Party Tool to Remove Outlook Duplicates

For overcoming the limitations and discovering a smart method to delete Outlook duplicates with ease, the best way is to use a third-party product, which is easily available in the web market. These tools are generated with the aim of removing duplicate items from Outlook PST files. One such tool is MS Outlook Duplicate Remover. This tool removes duplicate emails, contacts, calendars, journals, tasks, and notes, from Outlook data files in a very effective manner. It supports both UNICODE and ANSI files to remove duplicate emails from multiple PST files in batch. It comprises of all useful features, which are widely used for deleting duplicate items from a PST files.


After having a vast discussion on Outlook Duplicate and measures to delete them, one can wind up with the fact that the smart way to delete duplicate from Outlook with ease is to use third-party tool i.e. Outlook Duplicate Remover. Since the remover deletes all the duplicate items within just few minutes and requires a couple of clicks, therefore, it is the best way to use Outlook Duplicates Remover.

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