How to Delete Duplicate Emails in Outlook PST 2021 or any Older Version?

  

Published By Jamie Kaler 

Approved By Rollins Duke

Published On July 8th, 2025

Reading Time 7 Min Read

Learn how to Remove Duplicate Emails from PST as it not only helps to maintain your mailbox size, but also improves efficiency and reduces the risk of losing crucial emails. In this guide we will explore all effective approaches to delete duplicate emails in Outlook using Outlook native feature and also share Outlook Duplicate Items Remover to easily remove and stop duplicate emails in Outlook.

What Causes Duplicate Emails in PST File?

• Incorrect configuration or multiple Outlook rules can create duplicate emails in Outlook PST file.
• If the mail server is unstable and Outlook is set to sync frequently then it creates duplicate emails in the PST file.
• Importing PST files to Outlook without enabling duplicates can create duplicate emails to flood your inbox or folders.
• Some Antivirus programs scan incoming emails and may interfere with Outlook’s normal sync process, accidentally creating duplicate emails in the process.
• Server-side issues especially with IMAP or Exchange can lead to incomplete sync and send emails multiple times into your mailbox.

What Makes this Tool Stand Out?

• This software is also a reliable tool when user want to remove duplicate emails from directly configured Outlook files.
• It offers a user-friendly interface to make it reliable software for all professional and individual users.
• You can also remove duplicate emails, contacts and remove duplicate calendars from Outlook.
• With this wizard, you can also use advanced filter options such as selective export, date range, from, to, subject, saving folder naming, exclude empty folder, separate PST per user, change language, export only selected Outlook items and so more.
• With this wizard, you can easily select a specific folder to remove duplicate emails from the PST file.

How to Delete Duplicate Emails from PST File Using Outlook Inbuilt Feature?

Let’s know what Outlook offers to remove duplicate emails from Outlook. Let’s see the techniques as we have shared below:

Method 1. Use Outlook Clean Up Tool

1. Open Outlook and Navigate to Inbox or any folder with duplicates.
   
2. Click on the Home tab and in the Delete Group.
   
3. Press on Clean Up and Choose One of the following: Clean Up Conversation, Clean Up folder or cleanup folder and subfolder as needed.
   
4. Confirm and press on Clean Up.
   

Method 2. Import/Export PST Method to Avoid Duplicates

1. Open Outlook and navigate to the file.
   
2. Click on open and export and press on Import/Export.
   
3. Select Import from another program or file and tap on Next button.
   
4. Browse Outlook data file and hit the Next button.
   
5. Choose the PST file as you wish to remove duplicate emails in the PST file.
   
6. Browse the destination path and check on do not Import duplicates then tap on the finish button.
   

Advanced Options

If Outlook inbuilt tools do not work correctly then technical users can use PowerShell Script to remove duplicate emails from the PST file. These advanced tools are ideal for large mailboxes or removing duplicate emails from Outlook.

Option 1. Use PowerShell Scripts for Bulk Duplicate Removal

1. $namespace = $outlook.GetNamespace(“MAPI”)
2. $inbox = $namespace.GetDefaultFolder(6)
3. $items = $inbox.Items
4. $items.Sort(“[ReceivedTime]”, $false)
5. $hashSet = @{}
6. $deletedCount = 0
7. for ($i = $items.Count; $i -ge 1; $i–) {
8. $item = $items.Item($i)
9. if ($item -is [Microsoft.Office.Interop.Outlook.MailItem]) {
10. $key = $item.Subject + “|” + $item.SenderEmailAddress + “|” + $item.ReceivedTime.ToString()
11. if ($hashSet.ContainsKey($key)) {
12. $item.Delete()
13. $deletedCount++
14. } else {
15. # First instance – store key
16. $hashSet[$key] = $true
17. }
18. }
19. }
    

Option 2.Remove Duplicate Emails from PST File Using VBA or Thunderbird Add-ons

You can use Outlook VBA Macros to remove duplicate emails as per date, subject, sender, recipients

VBA Advantages

• Outlook offers inbuilt VBA to easily use it without installing any other applications.
• Allows to select duplicate emails as per specific data.
• Reusable for other Outlook Cleanup Tools.

External Apps like Thunderbird Add-ons

• Thunderbird with deduction add-ons can import PST and detect duplicate emails during conversion.
• Useful for migrating from Outlook to Thunderbird.

Preventing Tips for Outlook Duplicate Removers

• Misconfigured rules can copy emails into duplicate folders. Navigate to Home and click on Rules and hit on Manage Rules and Alerts and review your consolidated overlapping rules. Use Stop Processing More Rules when needed.
• Set your sync interval to 15-30 minutes(not less than 5) to prevent server overload and duplicate downloads. Find this under file and tap on options and hit on Advanced and press on Send/Receive Settings.
• Email scanning features in Antivirus programs can cause duplicates. Disable email protection or exclude Outlook files in your antivirus settings.

Ending Remarks

We hope after reading this guide, you got the accurate solution to remove duplicate emails in Outlook, as we have shared techniques for all users, starting from beginner, medium, and advanced technical users to easily delete duplicate emails in Outlook. If you want instant output and don’t want to invest much effort, we recommend you to choose the automated solution, as it is specially known for faster results and can easily handle any number of PST files without passing any restrictions.