How to Remove Duplicate Items in Microsoft Outlook?

Siddharth Rawat
Siddharth Rawat | Updated On - 08 Apr 2022 |

Read time 10 minutes

When you import items in MS Outlook, and the duplicate detection option is turned off, and this is where Outlook skips the duplicate items. Once the import is completed, you cannot remove duplicate items easily. Focus on the phrase “you cannot remove duplicate items easily.” This means – you can remove the duplicate items, but not easily.

To help you remove duplicate items in Microsoft Outlook 2016, 2019 and in all previous versions, go through this entire post meticulously.


Instant Solution

Try automated tool Kernel for Outlook Duplicates Remover to quickly detect and remove duplicate items from your Outlook PST mailboxes.

How Duplicate Items May Become Problematic for You?

Microsoft Outlook is counted among the prominent applications offered with Microsoft Suite. For ensuring smooth performance, Outlook requires loads of resources. Outlook users commonly encounter duplication of messages and emails from time to time. You will probably be facing the below-mentioned problems at some point in time.

  • Duplicate emails lead to confusion. The user cannot confirm whether an email was replied or not. If you continue to reply the same email multiple times, then it will lead to further confusion between the team members and clients.
  • Duplicate emails increase the size of the Outlook data files unnecessarily. The Outlook application becomes slower. It negatively affects the business productivity. It takes more time in accessing new emails and replying to them.
  • If the Outlook is configured with Exchange Server or Office 365, duplicate items will increase the size of Exchange/Office 365 mailbox.
  • The Outlook backups will take more space and if you save backups at any external cloud storage, then you will need to pay more for extra space.

Reasons That Result in Duplication of Email Messages

The reasons are many, and the possible reasons are listed below.

  1. Incorrect configuration of rules
    If the rules are configured incorrectly, it will create confusion when you receive an email message. This results in duplication of the emails.
  2. Short intervals in sending and receiving messages
    If the inbox updates with low frequency, the emails and other data in the mailbox will not get synchronized and will lead to duplication of data.
  3. Error in account setup
    If the same email account is used in different devices, i.e., laptop and mobile, then it will cause repeated synchronization of the incoming message. This can be one of the reasons for email duplication in the Outlook mailbox.
  4. Inappropriate settings of the mailbox
    While creating an account in Outlook, if the mailbox parameters are set inappropriately, then it is likely to receive same email and any message for multiple times.
  5. Technical Issues
    The technical issue in the mail server is also a reason behind the duplication of Outlook items. Such instances frequently happen if you activate the option of “Leave Messages on the Server”. The inaccurate configuration of Microsoft Outlook gets regulated when two or more “move a copy to” rule is applied to specific incoming emails. This often leads to duplication of emails. Duplication of emails can also be due to the merging of numbers of PST files into a single file.

Whatsoever may be the reason behind creating multiple copies of a single message, it will hamper the productivity of Microsoft Outlook, and therefore, you should remove duplicate items of Outlook!

How to check the duplicity of emails in Outlook?

You cannot determine the duplicity of a single outlook email in a single glance. You can use several properties of a message to check if it shows more than a single email. You can use the following fields for the comparison:

  • Subject
  • Text
  • Sender
  • Recipient
  • Attachment

If you run a search using such fields, you can see the same emails multiple times if you have duplicates in the mailbox. For a small number of duplicate emails, you can search the inbox emails based on the above fields (e.g. “Subject”) and delete the similar emails using the Delete option in the application. But the same would be a tough task when there are a large number of duplicate items.

Is It Easy to Remove the Duplicate Files from Outlook 2019, 2016, 2013, 2010, and 2007?

Cleaning the duplicated files from your mailbox is essential. It would be tough for you if you have hundreds to thousands of such items. If the count is even bigger, it would be almost impossible to delete those items manually. So, in short, removing duplicate items manually is not an easy task, and unfortunately, Microsoft does not provide an easy fix for this problem, not even in Outlook 2013.

How to Remove the Duplicate Items On Outlook?

Do you want to eliminate the duplicate emails from your Outlook?

Before you get ready to remove the duplicate items of Microsoft Outlook, you need to find the cause of the problem and then solve the problem. However, if you cannot do anything, then here is the help for you. Below mentioned are five ways to remove duplicate files from Outlook mailbox.

1) Configure the rules correctly
Check whether the Outlook rules are configured correctly or not. If rules are not set appropriately, it will create confusion among different email folders. Configure the rules correctly. Also, ensure that only a single instance of the Outlook application is running. Close the extra instances of the Outlook.exe using the Task Manager on your system.
2) Always select “Do not Import Duplicate Items” while importing Outlook items
When you import of Outlook PST file items like mailbox folder or contacts using the Import/Export feature in the Outlook application, you must ensure to select the “Do Not Import Duplicate Items” option towards the end of the Import process to avoid the import of duplicate items in the application
3) Set the inbox updates frequency
You need to increase the inbox update frequency. Start Outlook and then go to Send and Receive. Now select Define Send or Receive Groups. Now set the value within 15-30 minutes.
4) Clean up the inbox
Outlook has numbers of utilities and add-ins, which can help you to clean-up the duplicate emails easily. Perform the below steps to clean up your mailbox:

  1. Start Outlook.
  2. Select a mailbox folder.
  3. Select Home > Cleanup. Now, configure the below options:
    • Clean up Conversation will delete and move the duplicate emails that are in the conversation.
    • Clean Up Folder will remove the duplicate emails from any particular folder
    • Clean Up Folders and Subfolders will clean up the duplicate folders and subfolders
  4. Right-click the Deleted Items folder and click Empty Folder that will permanently delete the emails.

5) Antivirus Application
If you found duplicate files in your mailbox, it could be due to the closing of the server connection and settings of the Antivirus application. If the server connection is not shut down properly, then emails that are not flagged as received will create the duplicates. For resolving this, you need to go through the manual of Antivirus application and disable the email protection. We do not recommend this step as disabling the antivirus can result in severe issues if any virus attacks your PC via an email.

6) Third-Party Outlook Duplicates Remover
You can also opt for a reliable Third-Party Outlook Duplicate Remover tool for permanently removing the Outlook duplicates. The third-party tools are developed in such a way that you do not need to worry about duplicate emails or other duplicate Outlook items anymore.

One such application is Kernel for Outlook Duplicates Remover. The software automatically finds and removes duplicate items from your Outlook. It is the best and proven solution to remove Outlook duplicate items. It provides you many options to find duplicate items; for example, you can specify a date range to find duplicates. A free version of the software is also available that allows you to remove duplicate items. You can also remove ten items from each folder with this free Outlook Duplicates Remover tool.

Follow the step by step process to remove duplicates in MS Outlook:

Step 1: Launch Kernel for Outlook Duplicates Remover application and click on the Add Task button to add or create a new task.

add or create a new task

Step 2: In the Task Creation Wizard, give Task Name and Task Description and click Next to proceed.

Task Creation Wizard

Step 3: Now, search for duplicate items by selecting folders; you can prioritize the folders to search for duplicate items with the Up and Down buttons and click the Next button for the next step.

search for duplicate items

Step 4: Choose the type of operation that you want to perform on the duplicate items searched by the software and click Next.

choose operation

Step 5: In this step, you can compare the emails and other items by selecting the properties as shown in the screenshot. Click on the Next button for the final step.

selecting the properties

Step 6: If you want to save the progress report of the task, click Save Report and finally hit the Finish button.

save the progress report

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As you have noticed, there is no manual solution to find and delete duplicate items in Outlook except that you read every email and delete them. To save your valuable time, you can opt for an automated solution like Kernel for Outlook Duplicates Remover.


Duplicate items can create a lot of issues in Outlook. They create confusion for users, consume large space in the data file, and even make PST files vulnerable to corruption issues and errors. Though Outlook users can take various precautions to avoid this issue, it is difficult to remove duplicate emails from the mailbox unless you are using a professional tool. That is why many Outlook users prefer Kernel for Outlook Duplicates to remove duplicate items from their mailboxes

Watch Video: To know Complete Process of Outlook Duplicates Remover Tool