Remove Duplicate Emails From Outlook

Why do Duplicate Emails Appear in Outlook?

Microsoft's pages and community threads name four causes:

• Sent mail is saved twice. Microsoft's article on IMAP accounts says the provider's server saves a copy of every sent message and Outlook uploads the same message again.
• Replies repeat older mail. Microsoft's article on Conversation Clean Up calls a message redundant when a later reply repeats it in full.
• Mail sits in several folders. The February 2026 thread asks how to remove duplicate emails across multiple folders in Microsoft 365.
• Imports add second copies. The Outlook import wizard has an option that excludes duplicates from a PST file.

Which Method Matches Your Duplicates?

Find your situation in the table:

5 Ways to Remove Duplicate Emails From Outlook

Methods 1 to 4 use Outlook settings. Method 5 adds software:

Method #1: Delete Redundant Replies Using Conversation Cleanup (Free)

Microsoft's article on Conversation Clean Up moves a message to Deleted Items when a later reply repeats it in full. Four steps clean a folder in classic Outlook:

1. Click the folder in the folder pane.
2. Select Clean Up from the Delete group on the Home tab.
3. Click Clean Up Folder for one folder or Clean Up Folder & Subfolders to include folders inside it.
4. Open Deleted Items and check the moved messages.

Note: On the simplified ribbon click the arrow next to Delete. Moderator says in the May 2026 thread that Clean Up ignores identical standalone messages. Backup the mailbox before you clean a large folder.

Method #2: Group by Subject and Delete the Copies (Free)

Independent Advisor advises grouping by Subject and deleting the copies when all of them sit in one folder. Six steps follow that reply in classic Outlook:

1. Open the folder with the copies.
2. Click View then View Settings and select Group By.
3. Clear Automatically group according to arrangement.
4. Select Subject under Group items by and click OK.
5. Open a group with two or more messages and compare the sender and the time.
6. Select the extra copies and press Delete.

Note: Independent Advisor says this works only for copies in the same folder. Empty Deleted Items after you check the result.

Method #3: Merge Mail With a PST Export and Import (Free)

Independent Advisor's reply also gives a route for classic Outlook accounts with a PST file or an Exchange mailbox.

Export the folder to a new PST file and delete the mail from the mailbox. Import the PST file back into the folder. Eight steps follow:

1. Create a backup of your Outlook data file.
2. Go to File then Open & Export then Import/Export.
3. Click Next after you select Export to a file.
4. Select Outlook Data File (.pst) and press Next then select the folder.
5. Name the new PST file and select Do not export duplicate items.
6. Open the new PST file and check the mail. Delete the mail from the original folder and empty Deleted Items.
7. Open Import/Export again. Press Next after you click Import from another program or file.
8. Select Outlook Data File (.pst) and then click Browse to open the new file. Tick Do not import duplicates and finish with Next then Finish.

Note: Independent Advisor says the export excludes copies only inside one folder. Select Do not import duplicates whenever you merge another PST file into a mailbox.

Method #4: Stop Duplicate Sent Items on an IMAP Account (Free)

Moderator pointed to Microsoft's article on duplicated IMAP sent messages when asked about copies in Sent Items. Microsoft explains that the server and Outlook both save the sent message. Four steps stop the second copy:

1. Select File then Account Settings then Account Settings.
2. Select the IMAP account and click Change.
3. Tick Don't save copies of sent items.
4. Click Next then Done.

Note: Microsoft states that the workaround does not always fix the problem. Sent Items can also lose the Bcc recipients with some providers. Delete the copies already in Sent Items with Method #2.

Method #5: EmailDoctor Outlook Duplicates Remover Software Finds Exact Copies Across Folders (Software)

Outlook has no built in remover for exact copies in many folders. EmailDoctor Outlook Duplicates Remover software finds duplicate emails and attachments plus calendars and contacts and notes.

According to EmailDoctor, the software works without Outlook installed. Work on a copy of the PST file.

Add the PST Copy and Select the Scope

Three steps prepare the scan:

1. Open the software and add the PST copy with Add File(s). Add Folder and Search Files add several files at once.
2. Select Across Folder(s) to compare mail between folders or Within Folder(s) to compare inside every folder. Click Next.
3. On the Select tab choose the folders. Then click Change for the Destination.

Set the Match Rules and Process the Copies

Three steps finish the setup:

4. Choose the item types in the Filter tab.
5. Open Specify Duplicate Criteria and tick the fields to compare. Click Save.
6. Select an action for the copies and click Next then OK.

Note: EmailDoctor names no demo limit for the software. Process one copied folder first and check the result before you buy a license.

What Did Your Duplicates Tell You?

Match your finding to the next step:

Frequently Asked Questions

Author’s Verdict

You remove duplicate emails from Outlook by matching the method to the copy. Clean Up fits redundant replies and grouping fits one folder.

Stop the second Sent Items copy with the IMAP setting. Use the PST export and import when you merge files.

Use duplicate remover software when exact copies span folders. Create a backup before you delete anything.