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3 Free and Easy Ways to Delete Duplicate Emails in Outlook

Written By Kristian Wilson
Marco Devin
Approved By Marco Devin  
Published On December 16th, 2022

Dealing with the problems of an oversized mailbox, decreased functioning of your email client service, or a sudden lack of storage space? This could be all due to the piling up of duplicate emails in your mailbox. The problem can be tackled manually by removing duplicate emails in Outlook when you have a small number of emails in your inbox.

But imagine the magnitude of this happening in an organization with a daily exchange of thousands of emails. In such a large setup, the issue of email duplication can quickly go out of control, shutting down the entire email client application.

Though this problem can occur with any email client service, here we will specifically discuss it in the context of Microsoft Outlook. This blog will cover the causes of duplication of emails in Outlook, how it affects the general functioning of the application, ways to prevent it, and the solutions to delete duplicate emails from Outlook.

Causes of Duplication of Emails in Outlook

To handle the issue of email duplication effectively, we must first understand the causes of its occurrence:

  • Incorrect Synchronization Settings: Configuring the Outlook account on multiple devices, such as desktop and smartphone, with the same user credentials can make the incoming data synchronize multiple times. It leads to receiving the same email more than once in your Inbox.
  • Incorrect Setting of Outlook Rules: Outlook is an email client service used to share data across multiple platforms and you need to set certain rules for the application to work properly. Any error in setting these rules can lead to the generation of duplicate emails. Hence, many users end up searching for how to remove duplicate emails in Outlook.
  • Incorrect Setting of Send/Receive Frequency: Incoming emails need some time to synchronize on the server and appear in your mailbox. If the frequency of your running the Send/Receive command is set short, then it might result in the same mail getting synchronized, again and again, resulting in duplicate emails.
  • Interruption by Antivirus Software: Sometimes the antivirus installed on your computer can intercept the working of the Send/Receive command. This may lead to emails being synchronized multiple times and hence the generation of duplicates.
  • Corrupt Emails or Server Problems: Any sort of corruption in the emails or the server can give rise to all sorts of problems, data duplication being one of them. In such cases, users find solutions to delete duplicate emails from Outlook. If you have a corrupt PST file, you can find out guide to repair Outlook PST files.
  • Incorrect Mailbox Setup: Another possible reason can be the incorrect setup of your Outlook mail account. In such a case, all the mailbox components will appear multiple times in your account.
  • Importing and Merging PST Files: Importing or merging PST files can sometimes override file/mailbox settings that may lead to redundancy of data items.

Effects of Duplicate Email in Outlook

Generation of duplicate copies of emails in a mailbox, whether personal or affiliated with a business account, has always been a cause of concern as it:

  • Mitigates Performance: Redundant data items in a mailbox overload the application, which starts hanging and freezing.
  • Slows down the System: Duplicate items lead to less space in the mailbox, adversely affecting the speed of email processing.
  • Consumes Time & Effort: Removing redundant emails from Outlook manually demands significant time and effort on the user’s part.
  • Damages Mailbox: A large number of emails in an overstuffed mailbox can lead to data corruption. This could eventually result in damaging the entire mailbox.
  • Causes Loss of Business & Goodwill: Outlook is utilized as one of the primary means of official communication by various organizations, so any sort of delay can cost them not only business but, sometimes, also goodwill.

How to Prevent Outlook from Duplicating Emails

It is said that prevention is better than cure. So before moving on to the solutions to delete duplicate emails from Outlook mailbox, let’s go through some of the ways in which you can prevent the generation of duplicate copies of emails.

1. Ensure that you do not set up any conflicting rules or filters while configuring Outlook. This is one of the most common causes of duplication of emails.

2. If there is more than one email account configured with the same credentials, delete one of them. You can check the number of accounts configured on your system from the Accounts Settings screen. Remove the one with a similar email address. This might end the need to remove redundant emails in Outlook.

3. Set the incoming email frequency to no less than 15 minutes. To access, ‘Schedule an automatic send/receive every’ box, first, click the Send/Receive button >> Define Send or Receive Groups.

4. Check the option to avoid duplicates every time you import a PST file into your Outlook Mail account.

5. Configure Antivirus settings in a way that does not obstruct incoming/outgoing Outlook messages.

Free Solutions to Remove Duplicate Emails in Outlook

Method 1: Check Outlook Account Settings

Sometimes, we configure the same Outlook account or import a PST file multiple times. This leads to the creation of duplicate data items. To remove this redundancy, perform the following steps:

1. Open the Microsoft Outlook application.

2. Click File > Info > Account Settings to open the Account Settings window.

3. Select the Email tab and check all the accounts configured in Outlook.

4. Select the redundant Email account, if any, and click the Remove button. This will delete the duplicate email account in Outlook.

5. Click the Close button.

Method 2: Use Import/ Export Feature

To remove duplicate email messages in Outlook via Import/Export option, follow these steps:

1. Open Microsoft Outlook.

2. Click File >> Open & Export >> Import/Export.

3. Select “Import from another program or file” option from the Import and Export Wizard and click Next.

4. Select “Outlook Data File (.pst)” from the Import a file window of the wizard and click Next.

5. Browse the PST file from which you wish to delete duplicate data and check the Do not import duplicates option from the Import Outlook Data File window. Click Next to move on.

6. Select Outlook Data File whose data you wish to export and click the Finish button.

Method 3: Use Clean Up Tool

MS Outlook provides the Clean Up tool to help you delete redundant emails from Outlook.

Follow these steps to use the Clean Up tool in Outlook:

1. Open Microsoft Outlook.

2. Click the Clean Up tool from the ribbon and expand all the options.

It gives you three options to choose from Clean Up Conversation, Clean Up Folders, Clean Up Folders & Subfolders

3. Select the Clean Up Folders & Subfolders option.

The Clean Up Folder dialog box will appear, asking you whether to proceed with the clean-up or cancel the task.

4. Click the Clean Up Folder option.

5. Click the Settings option and manually enter the Deleted Items location.

6. Click the Browse button on the Outlook Options window will open to add the PST file.

7. Click Deleted Items→ OK from the Select Folder window.

8. Click the Clean Up Folder option to remove all duplicate emails from your Outlook mailbox.

Limitations of Manual Methods

Manual methods are feasible only if you have a small number of emails in your mailbox. These solutions are not recommended if you have a large-sized PST file due to the following reasons:

  • Identifying and removing duplicate emails from a huge mailbox is a tedious and error-prone task.
  • The Clean Up tool also does not work very effectively on an overcrowded mailbox. It is reported to generate the error message “No messages were cleaned up. Only messages that satisfy your clean-up settings will be moved to the trash folder.”

To overcome these limitations and remove duplicates from your Outlook mailbox effortlessly, you should go for a professional automated solution.


In this article, we have discussed the issue of duplicate emails in Outlook. The problem, if not checked, not only slows down the performance of the email client service but can also cause major damage to the mailbox. This blog also explained the main causes of the generation of duplicate emails as well as solutions to remove duplicate emails from Outlook. Manual solutions come with their limitations to surpass and a professional duplicate mail remover tool is recommended.