How to Stop Receiving Duplicate Emails In Outlook

Last updated on August 2nd, 2025 at 10:58 am

Tired of seeing duplicate emails? It’s understandable.

Duplicate emails create inbox clutter and can have you missing out on important emails due to the disorganization. Not to mention the waste of time reading the same message multiple times. 

While duplicates seem complicated to resolve, there are quick steps you can use to have your inbox clean and prevent duplicates from happening again.

Read on to understand why you have been receiving duplicates and how to stop receiving duplicate emails in Outlook in easy steps. 

Why You Are Receiving Duplicate Emails In Outlook

Before getting to the solutions, here are some reasons why you receive duplicate emails in Outlook. 

Synchronization Problems

To receive emails on Outlook, you must communicate with your email provider, such as Gmail or Yahoo. 

Outlook can download the same email multiple times if there is a breakdown in the synchronization.

For example, if your internet connection drops during Outlook syncing, it might not record downloaded emails, but you can retrieve the email once the connection resumes.

In other instances, email servers can delay marking emails as delivered, making Outlook interpret the emails as new, causing duplication. 

Misconfigured Email Rules

Outlook has rules and alerts that are critical in email automation. If the rules are incorrectly set up, it can cause duplications.

For example, if you have a rule that forwards to yourself in another folder and keeps a copy in the inbox, you will likely see duplicates.

Also, if multiple rules are being processed in the same email, it can appear in different folders or simultaneously be in the same folder.   

Multiple Devices Syncing the Same Email

Use Outlook on multiple devices, such as your tablet, laptop, and phone, or accidentally add the same email multiple times.

Each device can download the same email independently, which can cause duplicates. 

Corrupt Outlook Data File

Outlook stores emails in data files, and if the files have some form of corruption, it can cause email duplication. Some of the signs to look out for when there is a corrupted data file are: 

• Outlook running slowly
• Error messages
• Outlook freezing 
• Duplicates appear after deleting

Add-Ins Interference

If you use add-ins such as backup software, an anti-spam plugin, or CRM tools, they can interfere with email processing and create duplicates.

For example, CRMs such as HubSpot can create email copies for tracking purposes. Also, misconfiguration of email backup tools can cause re-importation of emails. 

Incorrect Email Forwarding

If you use email forwarding or have several aliases for the same account, Outlook might treat them as separate emails.

In addition, if your email provider forwards messages to another address and you have both accounts in Outlook, you’ll get duplicates.

How to Stop Receiving Duplicate Emails In Outlook

If you are experiencing duplicate emails in Outlook, you can try this to fix it: 

Check and Adjust Sync Settings

You can fix synchronization issues that cause email duplication by:

1. Open Outlook and go to File, then Account Settings 
2. Select your email account and click Change.
3. Under More Settings, go to the Advanced tab.
4. Look for Download Shared Folders or Cached Exchange Mode settings.
5. If Cached Exchange Mode is enabled, turn it off temporarily to see if duplicates stop.
6. Click OK and restart Outlook.

If you have a Yahoo or Gmail account, try this:

1. Go to File, then Account Settings 
2. Select your IMAP account and click Change.
3. Under More Settings, go to the Advanced tab.
4. Ensure the option Leave a copy of messages on the server is unchecked (unless you need it for backups).
5. Click OK, then Next, then Finish, and restart Outlook.

Reset Your Email Account

To fix duplicates in Outlook, you can reset your email account by disabling and re-enabling it.

The action forces Outlook to re-sync with the server to fix duplicate issues. Try this: 

1. Go to File, then Account Settings
2. Select your email account and click Remove.
3. Restart Outlook.
4. Go back to File, then Add Account and re-add your email.

Fix Email Rules

Rules that move forward emails can sometimes cause duplicates. Here’s how to check and fix: 

1. File then Manage Rules & Alerts.
2. Review all active rules and look for any that might forward emails to you or move them multiple times.
3. If you find an incorrect rule, select it and click Delete or Disable Rule.
4. Click OK and test if duplicates still appear.

Fix Outlook File Corruption

Having corrupt Outlook files can cause persistent duplicates. To fix this, you can run the inbox repair tool: 

1. Close Outlook.
2. Search for SCANPST.EXE in your Windows Start menu.
3. Open it and browse your Outlook data file
4. Click Start to scan for errors.
5. If you find errors, click Repair.
6. Reopen Outlook and check for duplicates.

Sometimes, even after running the inbox repair tool, you still experience duplicates. In this case, try: 

1. Go to Control Panel, then to Mail, and then to Show Profiles.
2. Click Add to create a new profile.
3. Set up your email again.
4. Set the new profile as the default and restart Outlook.

Auto Remove Duplicate Emails

Outlook has built-in tools to help you clean out already existing emails. To clean them out, try this: 

1. Select your inbox.
2. Go to the Home tab, click Clean Up, then Clean Up Folder.
3. Outlook will remove exact duplicate emails.

You can also search and clean up the duplicates manually: 

1. Click the Search bar in your inbox.
2. Type the common subject line from duplicates.
3. Sort by date or sender to identify duplicates.
4. Select the duplicates manually and press Delete.

Disable Add-ins

If you have some Outlook add-ins that could be causing duplicates, you can disable them by: 

1. Go to File, then Options, and then Add-Ins.
2. At the bottom, select COM Add-ins and click Go.
3. Uncheck all add-ins and click OK.
4. Restart Outlook.
5. If duplicates stop, re-enable add-ins individually to find the corrupt one.

How to Prevent Future Duplicate Emails in Outlook

To ensure that duplicate emails do not come back after cleaning them up, you can apply these tips:

Reviewing Rules and Alerts

Establish a routine to check for conflicting Outlook rules. Go to file, manage rules and alerts, and look for rules that move emails to multiple folders, or forward emails without deleting the original version. 

Test each rule individually to identify specific conflicting rules. After testing, delete or change unnecessary ones.

Other tips to manage Outlook rules:

• Stop processing more rules to prevent the same rule from applying to multiple emails
• Ensure there is no overlap between Outlook rules and server rules

Have a Stable Internet Connection

You need a stable internet connection for Outlook to sync emails correctly. Internet instability can cause emails to be re-downloaded, leading to duplication. 

You can use a wired internet connection when experiencing unstable Wi-Fi. An Ethernet connection is more reliable and stable than a wireless connection. 

When experiencing a weak internet connection, pause Outlook syncing by working offline or avoid being on Outlook until the connection regains stability. 

Also, adjusting sync frequency to longer intervals can help minimize the occurrence of duplicates due to internet issues. 

Don’t Add the Same Account Multiple Times

You will have duplicates if you can check emails from multiple devices on your Outlook account. To prevent this: 

• Check whether your email account is listed once in the Outlook settings
• If you have numerous devices, ensure only one can download emails immediately
• Do not add the same account as IMAP and Exchange to prevent duplicate email downloads

Update Outlook

Having regular Outlook updates can prevent duplicate email problems. Ensure that you have auto-updates for your Outlook and also schedule manual updates.

Also, remember to use the latest Outlook version to avoid old bugs that can cause duplicate emails. 

Maintain Outlook Data Files

You must maintain Outlook data files to prevent corrupted PST (POP3) or OST (Exchange/IMAP) files from causing duplicates. 

For example, you can run the inbox repair tool on schedule to check for errors. Also, when you need to leave Outlook, avoid false exiting. Instead, leave properly – (file, then exit).

Also, compact the PST files by: File > Account Settings > Data Files > Settings > Compact Now. Compacting prevents the risk of duplicates by reducing file bloat. 

Manage Problematic Add-Ins

While you need add-ins for your Outlook, sometimes, they can be problematic and cause duplicates. 

You can manage add-ins by temporarily disabling:

1. Go to File > Options > Add-Ins > COM Add-ins > Go.
2. Uncheck all, then restart Outlook.
3. If duplicates stop, re-enable add-ins individually to find the problematic one.

If you know the specific problematic add-in, individually remove it to prevent further duplicates.

Quick Checklist To Prevent Duplicates

• Check for conflicting/misconfigured rules on schedule
• Have stable Internet and avoid syncing on weak connections.
• Single Account Setup. Avoid adding the same email twice.
• Update Outlook by installing the latest patches.
• Maintain Data Files by running SCANPST occasionally.
• Manage Add-Ins by disabling problematic plugins.
• Perform server Settings by adjusting IMAP/Exchange retention.

Final Take 

Duplicate emails can be a pain, but they are fixable. The issue could be problematic add-ins, internet instability, or misconfigured rules. 

You can fix duplicate issues by removing problematic add-ins, using Outlook on a stable internet connection, deleting duplicates, or avoiding double logins. 

Remember, even after fixing the duplicate emails, take the necessary steps, such as maintaining data files, to prevent the recurrence of duplicates.