How to Remove Duplicate Items from Microsoft Outlook?

If you use Microsoft Outlook, you must have faced problems with similar items in your mailbox, such as emails, calls, lists, and many other similar items. Printing can be confusing when receiving and sending e-mail. Therefore, most Outlook users want to know how to protect and remove duplicate items from Microsoft Outlook  2019, 2016, 2013, 2010.

In addition, multiple recycling devices can increase the size of the mail file. If your mailbox reaches this size, you will encounter illegal files.

So, if you want to solve data corruption and productivity problems with MS Outlook, read this article and learn how to prevent and remove duplicates in Outlook, in this blog Here we will talk about how duplicates appear in Outlook and how to remove duplicates from Outlook easily.

Why Do Duplicate Items Appear in Outlook Mailbox?

There are many things that can cause duplicates in Outlook, such as Outlook errors, errors or incorrect users, etc. Below are some causes of duplicates in Outlook.

  • The mobile phone does not sync with the desktop version of Outlook.
  • Receive and send email regularly
  • Incorrect Outlook rules
  • Import or combine multiple PST files into one.
  • Restore your mailbox from backup
  • Use a mailbox on multiple devices
  • Use antivirus software with email scanning capabilities

How to Duplicate Items Cause You Problems?

  • Microsoft Outlook is one of the main applications offered by the Microsoft Suite. To ensure performance, Outlook requires a lot of resources. Most Outlook users experience overlapping messages and emails from time to time. You may experience the following problems from time to time.
  • Duplicate emails can be confusing. The user cannot confirm whether the email has been replied to. If you keep replying to the same email over and over again, it will cause more stress between partners and customers.
  • Duplicate emails can increase the size of Outlook’s file system unnecessarily. The Outlook application is slow. This has a negative impact on the manufacturing industry. It takes more time to access new emails and reply to them.
  • If Outlook is installed with Exchange Server or Office 365, the corresponding item will increase the size of the Exchange / Office 365 mailbox.
  • Outlook backups take up a lot of space, and if you store your backups on an external cloud storage, you will have to pay more for the extra space.

How to Identify Remove Duplicate Items from Microsoft Outlook?

You cannot show all Outlook email copies on one side. It can use multiple properties to control whether messages show multiple email addresses. You can use the following fields for comparison:

  • the meaning
  • Text
  • the sender
  • Customers
  • Continued

If you search using these fields, you may see the same email multiple times if you have duplicate messages in your mailbox. For a small number of duplicates, you can search your inbox according to the fields above (such as “Subject”) and delete similar emails using the app’s delete option. But if there are many parallel projects, this will be a difficult task.

How to Prevent or Remove Duplicate Email Items from Outlook?

As we said above, there are many things that can cause duplicates in Outlook mailboxes. So preventing this from happening in the future is the first step to eradicating it.

Solution #1: Stop Receiving Duplicate Emails

There are a few things you should check to stop receiving duplicates in Outlook. So check your Outlook rules first to make sure no copies are made to your inbox and make sure all your rules end with a “stop processing” action.

Always remember that your task manager only runs one Outlook instance. Running two instances of Outlook can result in two messages arriving at the same time.

Solution #2: Prevent Duplicate Emails From Sending

Third-party antivirus software is the reason for sending a lot of emails or overdoing it in Outlook. Some antivirus software scans outgoing email, so you may find duplicate emails in the Outlook Sent folder. Therefore, change the antivirus properties so that outgoing email is not scanned.

Solution #3 Avoid duplicates Appointments

Duplicate appointments were created because multiple Outlook processes were running during the synchronization process. To see if some process is running, exit Outlook and go to Task Manager and go to the Processes tab and look for Outlook.exe. To complete the process select it and finish the final process

Solution #4: Prevent Duplicate Contacts

When you import contacts into Outlook, if you forget to check the “No duplicate entries” option, the duplicate contacts will be saved in the Outlook Contacts folder. If you are importing mailbox data from another source, don’t forget to select the “No duplicate entries” option.

#1. Method Manual to Remove Duplicate Items from Microsoft Outlook 

Microsoft Outlook comes with a cleanup tool that helps you remove duplicate Outlook PST files. So, follow the steps below to use it effectively.

  • Open Microsoft Outlook
  • Now click on Cleanup Tool in the ribbon bar

select cleanup

  • Choose the option to clean folderssubfolders

choose folders

  • After you click Delete Folders and Subfolders, a dialog box will appear asking if you want to continue or cancel the cleanup. Just click on “Clean Up” Options

select cleanup option

Note: After the cleaning process is complete, all copies will be placed in the Deleted Items folder.

Automatic Solution to Remove Duplicate Items from Microsoft Outlook 2021, 2019, 2016, 2013, 2010

The manual method is a good method when the number of duplicates in Outlook is low. But we have a lot of iterative projects that require a lot of effort and time. And while using the cleaning tool, sometimes an error message appears like “Cleaning was not performed”. The manual process is good for those who have a few repetitive lists. But with many items to repeat, this method takes a lot of time. Because you must manually select a duplicate items entry from Outlook. Also, there is a high chance that the important text will be deleted.

Therefore, to complete this work, we propose the best automated solution, namely SysTools Outlook Duplicates Remover is a great tool for dealing with duplicate items. It is a smart software to remove duplicate items from Outlook i.e. emails, contacts, calendars, tasks, notes and journals. Users just need to add a PST file and the software will automatically detect and remove duplicate files with a few simple clicks.

Free Trail Demo Version: User can download the demo version of Outlook Duplicate Remover software and try it for free. Since this is the free version of the software, it has some limitations. It allows users to remove 15 items in per folder after removing duplicates from PST files. When enjoying the free version of Duplicate Remover for Outlook, the user can purchase the full version and have full access to the tool. There is no removal restrictions.

Follow these Step-by-Step Instructions to Remove Duplicate Items from Microsoft Outlook

  • First, install and Run the Software on your local machine

Outlook Duplicates Remover Tool

  • Now click Add File or Add Folder to add PST/OST/BAK files

Add PST Data items

  • Select Within Folder/ Across Folders Options

Choose folder options

  • Press the change Option to save the results to the PST, OST, BAK file of your choice

select destination

  • Check the boxes in the Choose Item Types section to delete all duplicate data from emails, contacts, calendars, journals, tasks, and notes

choose items type

  • After that, choose the action you want to perform

Select any Deletion options

  • After completing all the settings, click Next to start removing unnecessary items in Outlook

Start the process


For people who work in Outlook every day, repeating things can be very frustrating. Once you have created a copy in your Outlook mailbox, it is very difficult to delete it. Therefore, in order to make your work easier, in the above article we have discussed the best way to protect and remove duplicate items from Microsoft Outlook without data lost.

Read More: Delete Duplicates Password Protected from PST File

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