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Remove Duplicate Emails in Outlook

Microsoft Outlook is one of the most widely used email clients, trusted by individuals and organizations for managing emails, contacts, calendars, tasks, and more. However, as Outlook data grows over time, users often face a frustrating issue with duplicate emails, contacts, and calendar items. These duplicate items not only clutter your mailbox but also slow down Outlook’s performance, increase PST/OST file size, and make it harder to locate important messages.

Outlook duplicates may arise for several reasons: improper synchronization with Exchange/IMAP servers, accidental imports from PST/OST/EML files, incorrect rules or filter configurations, or technical issues during backups and migrations. Whatever the cause, removing duplicates manually is tedious and error-prone. This is where the EdbMails Outlook Duplicate Remover Tool comes in handy. It provides a fast, secure, and accurate way to scan Outlook mailboxes, identify duplicates based on customizable criteria, and eliminate them without data loss.

Remove duplicates from Office 365

In this guide, we’ll explore everything you need to know about removing duplicate emails in Outlook, including causes, challenges, step-by-step removal, planning, prerequisites, and post-cleanup best practices.

Common Causes of Duplicate Emails in Outlook
Understanding why duplicates occur is the first step toward preventing them. Some of the most common causes include:
1. Synchronization issues
  When Outlook is connected with Exchange, Office 365, Gmail (IMAP), or other servers, sync errors may result in duplicate messages.
2. Improper import/export operations
  Repeatedly importing PST, OST, or backup files into Outlook without filtering duplicates can create multiple copies of the same messages.
3. Rules and filter misconfiguration
  Incorrectly defined Outlook rules, forwarding settings, or spam filters may inadvertently duplicate incoming emails.
4. Multiple device access
  Accessing Outlook on laptops, desktops, and mobile devices simultaneously may trigger duplication during synchronization.
5. Server timeouts or interruptions
  Connection interruptions can cause Outlook to resend or redownload emails, leading to duplicate copies.
6. Third-party add-ins and plug-ins
  Certain Outlook add-ons or synchronization tools may duplicate messages while performing background operations.
7. Synchronization issues
  When Outlook is connected with Exchange, Office 365, Gmail (IMAP), or other servers, sync errors may result in duplicate messages.
8. Restoration from backups
  Restoring data multiple times from previous backups often introduces duplicates into Outlook folders.
EdbMails Outlook Duplicate Remover Tool
While Outlook provides some built-in features (like cleaning up conversations), they are limited in functionality and may not remove duplicates across all folders. EdbMails Outlook Duplicate Remover tool offers a complete solution with advanced features:
1. Supports all Outlook versions: 2021, 2019, 2016, 2013, 2010, 2007, and Office 365 connected Outlook.
2. Multiple matching criteria: Subject, Sender, Recipient, Date, Attachments, Internet Message ID.
3. Flexible actions: Soft Delete (mark as deleted), Hard Delete (permanent removal), or Move to Deleted Items.
4. Safe and non-destructive: Original mailbox data remains intact while only duplicates are removed.
5. Preview before removal: Verify detected duplicates before confirming deletion.
6. Detailed logs and reports: Know exactly how many duplicates were found and removed.
7. Optimizes Outlook performance by reducing file size and improving search efficiency.
Planning to remove duplicate emails in Outlook
Before performing duplicate removal, proper planning ensures accuracy and safety:
1. Identify duplicate sources
  Check whether duplicates were caused by imports, sync issues, or incorrect rules.
2. Choose target folders
  Focus on Inbox, Sent Items, Archive, and large folders most likely to contain duplicates.
3. Define duplicate criteria
  Decide whether duplicates should match subject, sender, date, attachments, or all combined.
4. Select removal action
  Move to Deleted Items for verification, Soft Delete for marking items, or Hard Delete for permanent cleanup.
Prerequisites Before Removing Outlook Duplicates
To ensure smooth deduplication, prepare the following:
- Download and Install EdbMails Outlook Duplicate Remover on your computer.
- Ensure Outlook is properly configured on your computer.
- Have account details to log in.
- Verify there are no ongoing sync operations with the mail server.
- For IMAP/Exchange/Office 365 mailboxes connected in Outlook, ensure network stability.
Steps to remove duplicate Emails in Outlook using EdbMails
Step 1: Download and Install the EdbMails application
- Download and install the EdbMails application on your computer running on Windows OS.
- Log in using your registered email address and password or choose the 'Start Your Free Trial'.
Step 2: Select Duplicate Remover product
- From the dashboard, choose ‘Remove Duplicates from O365. Exchange. IMAP’.
- Choose the option ‘Remove Duplicates from IMAP Mailboxes’ to proceed.
- You can proceed with the default job name or click ‘New Job’ to change.
- On the Settings page, choose how duplicates should be handled, move to Deleted Items, mark as Soft Delete, or permanently Hard Delete. You can also select matching criteria such as Internet Message ID, body content, or Subject/Date/From address. Once you’ve configured the settings, click ‘Next’ to continue.
Step 3: Connect Your Outlook IMAP Account
- To remove duplicates from a single user, select ‘Single User / Account Migration’.
- Choose the desired protocol (IMAP or POP3) and click ‘Next’ to continue.
- Select the IMAP hostname (imap-mail.outlook.com) in the list. Next, enter the email address and password of your Outlook, and click ‘Login’.
- To connect to multiple Outlook mailboxes, choose the ‘Multiple (Bulk) Users / Accounts Migration’ option and click ‘Next’ to continue.
- Click ‘IMAP Migration CSV File’.
- Choose the location to save the CSV file.
- Open the CSV file and update it with the required details such as Source Mailbox Name, Password, Host, and Port Number.
- Save the changes and close the CSV file.
- Click on the ‘Browse CSV File’ button.
- Select the modified CSv file and click ‘Next’.
- Choose the mailboxes or folders you want to include in the duplicate removal process, and then click ‘Next’ to continue.
Step 4: Verify Mailboxes
- Review the list of selected mailboxes and confirm that the Action is set to ‘Remove Duplicate’.
- Click on the ‘Start’ button to initiate the duplicate removal operation.
Step 5: Monitor and Confirm Removal of Duplicate Emails
- A progress bar will display the status of the duplicate removal process. Once completed, a confirmation message appears.
- Click ‘View Log’ to see a detailed report of how many duplicate emails were removed.
- Finally, sign in to your Outlook account and verify the items
Post-Duplicate Removal Process
- Check the Deleted Items folder: Ensure important emails were not mistakenly moved.
- Review log reports: Cross-check duplicates identified and removed.
- Adjust Outlook rules/filters: Correct misconfigured settings to avoid recurrence.
- Monitor synchronization: Ensure proper sync with IMAP/Exchange servers.
Preventing Future Duplicates in Outlook
1. Avoid importing PST/OST files multiple times.
2. Configure Outlook rules carefully to prevent duplicate forwarding.
3. Regularly archive old emails to separate PST files.
4. Disable unnecessary add-ins that may cause sync conflicts.
5. Use reliable internet connections during sync to avoid download errors.
6. Perform periodic deduplication using EdbMails.