Outlook Sending Duplicate Emails – [Quick Guide to Fix the Issue]

Last Updated on August 9, 2023 by Amit Bansal

We’ve all been there: you hit “send” on a crucial email, only to find out that your recipient received not one, but several copies of the same message.

The duplicate email issue in Microsoft Outlook has left many users scratching their heads, facing confusion, or even embarrassment.

But what causes this frustrating glitch? And more importantly, how can it be prevented or resolved?

In this blog post, we’ll delve deep into the underlying causes behind Outlook sending duplicate emails and provide you with effective solutions to tackle the problem head-on.

Whether you’re a casual user or an IT professional, understanding this issue can save you from future communication snags.

Read on to discover how to keep your emails on track and avoid inundating your contacts with unintentional email clones.

The introduction sets the stage for a comprehensive discussion about the causes and solutions of the duplicate email problem in Outlook.

Understanding the Cause of Duplicate Emails

In 2023, many users still experience the issue of Outlook sending duplicate emails.

As we aim to provide a clear and knowledgeable understanding of this problem, we must first explore the possible causes behind duplicate emails in Microsoft Outlook and IMAP mail servers.

One contributing factor to duplicate email occurrences is an incorrect configuration of the Sent Items folder.

This may lead to multiple copies of sent items appearing in your email application.

To avoid this, ensure that your Sent Items folder is correctly configured to save only one copy of each sent email.

Another possible cause is related to the user’s mailbox settings on the mail server.

It is crucial to confirm that your mail server is working optimally and that your Microsoft Outlook email application is set up by your IMAP mailbox settings, as discrepancies in mailbox configuration may result in duplicate emails.

In addition to the factors mentioned above, users may also experience duplicate emails due to their own, specifically-defined rules within Microsoft Outlook.

For instance, if a user creates a rule to move messages from contact A to folder B, this could lead to duplicate messages appearing in both folders.

Therefore, users should double-check their Outlook rules and settings to prevent any duplication.

Occasionally, duplicate emails may be caused by a corrupt Outlook PST file. In cases such as this, it is essential to repair or recover the PST file in question to resolve the duplicate email issue.

Moreover, the presence of third-party add-ins and anti-virus programs might interfere with the Outlook email application’s ability to function properly.

It may be helpful to temporarily disable these applications and add-ins to verify if they are the root cause of your duplicate email problem.

In conclusion, understanding the possible causes of Outlook sending duplicate emails is essential to identify the most suitable solution for rectifying the issue.

We should pay close attention to our email application settings, server configurations, and any additional software that might interfere with the seamless operation of Microsoft Outlook.

By doing so, we can effectively prevent the occurrence of duplicate emails in our inboxes.

Common Reasons for Email Duplication in Outlook

There are several reasons why Outlook might be sending duplicate emails. In this section, we will discuss some of the most common causes and how they can be addressed.

One reason for duplicate emails in Outlook is the use of an IMAP account, such as Gmail, Yahoo, or AOL.

When IMAP accounts are configured in Outlook, the email server automatically creates an item in the Sent Items folder, while Outlook uploads the same item again.

This behavior often leads to duplicates appearing in the Sent Items folder.

Another reason for email duplication is incorrect account settings. If the settings are not configured properly, especially for IMAP accounts, it can lead to issues such as duplicated emails.

To fix this issue, users should remove and re-add the email account in Outlook, ensuring that the settings are updated and correctly applied.

Also Read: – Here is a tutorial on how to remove or delete an email account from Outlook.

Improper handling of attachments can also cause email duplication.

For example, if a mail with a large attachment is stuck in the Outbox, every time Outlook attempts to send the email, it may create a duplicate. To avoid this, ensure that your attachments are within the size limits set by your email provider.

POP3 accounts can also cause duplicated emails in Outlook, especially when multiple devices access the same mailbox.

If the option “Leave a copy of messages on the server” is enabled, it will cause multiple copies of the same email to be downloaded to your local folders.

To fix this, go to your account settings and untick this option for your POP3 account.

In some cases, email duplication might be due to a corrupt or damaged received email. When corruption occurs, it can cause the Send/Receive process in Outlook to generate duplicate emails.

To prevent this, users should ensure that their mailboxes are regularly maintained and errors are promptly addressed.

In summary, various factors can cause email duplication in Outlook, including account settings, IMAP accounts, attachments, POP3 accounts, and mailbox corruption.

By carefully managing each aspect, users can help prevent duplicate emails and maintain a more organized and efficient Outlook experience.

Different Versions of MS Outlook and Their Potential Duplication Issues

We understand the frustration that can come from dealing with duplicate emails in various versions of MS Outlook.

It is essential to pinpoint the causes and know how to fix them.

In this section, we will cover some potential duplication issues for Outlook 2021, Outlook 2019, Outlook 2016, and Microsoft 365.

Outlook 2021, the latest version, has enhanced performance and features. However, like its predecessors, it can still face issues with duplicate emails.

One possible cause could be related to the synchronization settings with your mail server. We recommend checking and adjusting your settings to ensure proper syncing.

Outlook 2019 also improved its performance compared to its older versions, yet the problem of duplicate emails may persist.

Often, the cause of the issue can be traced back to third-party add-ins that conflict with the regular functioning of Outlook.

Disabling unnecessary add-ins might help prevent the duplication of sent emails. Further guidance on this issue can be found here.

Outlook 2016, like the other versions mentioned, can experience duplicate email issues. One common culprit, in this case, lies within the inbox rules.

Misconfigured or conflicting rules may result in multiple copies of the same email. To resolve this, review and edit your inbox rules to prevent duplication.

Microsoft 365 users may also face the issue of duplicate emails. This problem is typically caused by a corrupted or outdated Outlook installation.

To resolve this, make sure your Microsoft 365 subscription is up to date and consider repairing your Outlook installation.

Overall, implementing these fixes and being mindful of potential duplication issues will help ensure a smoother experience for users of Outlook 2021, Outlook 2019, Outlook 2016, and Microsoft 365.

Remember, always keep your installation updated and periodically check for common causes of duplicate emails to ensure the efficient use of your email client.

Inspecting Your Account Settings

When using Outlook, sometimes we may experience an issue with duplicate emails being sent. This can be frustrating, and it’s essential to find a solution to this problem.

One of the primary causes for this might be related to the account settings.

In this section, we will discuss how to inspect and modify your account settings to prevent Outlook from sending duplicate emails.

First, let’s ensure that our account settings are correctly configured for an IMAP account. Outlook supports various mail account types, such as IMAP, POP3, and Exchange accounts.

If we’re using an IMAP account, it’s essential to make sure that our sent messages are correctly handled to prevent duplication.

To access your account settings in Outlook, simply go to File >> Account Settings >> Account Settings.

Here, you will find a list of all configured email accounts. Select the IMAP account you’re experiencing issues with and click on the “Change” button to view its settings.

Now, let’s focus on the Sent Items folder settings for our IMAP account. This is crucial because improper handling of sent items may result in duplicate emails.

In the account settings window, navigate to the “More Settings” button and click on the “Sent Items” tab.

Here, we should verify if we have selected an appropriate option for saving sent items.

When using an IMAP account, it’s generally recommended to allow the server to handle saving sent items rather than Outlook.

Additionally, you might want to consider checking the add-ins installed in your Outlook. In some cases, add-ins can lead to issues with sending duplicate emails.

To inspect this, go to File >> Options >> Add-ins >> Go. Here, you can disable any suspicious add-ins, which may be causing the problem.

By following these steps and carefully inspecting our account settings, we can effectively identify and resolve the issue of Outlook sending duplicate emails.

Remember, it’s essential to keep our email account settings optimized to ensure a seamless emailing experience.

Checking and Adjusting Server Settings

When dealing with Outlook sending duplicate emails, one of the first things we should check is our mail server settings.

Mail server settings determine how Outlook communicates with the email provider’s server, and incorrect settings may interfere with the sending process, leading to duplicates.

Firstly, we should verify our incoming mail server (IMAP or POP) and outgoing mail server (SMTP) settings provided by our email provider.

To find these settings, we can consult our email provider’s help documentation or contact their support team. Once we have the correct server settings, we can update them in Outlook as follows:

  1. Open Outlook and click on File in the upper-left corner.
  2. Choose Account Settings and then select Account Settings again from the drop-down menu.
  3. In the Account Settings window, click on the email account we wish to edit, then click Change.

Now we can update the Incoming and Outgoing mail server fields according to the information provided by our email provider.

Additionally, we may need to adjust the server timeout settings to avoid premature disconnections during the sending process, which could cause duplicate emails.

To adjust the server timeouts in Outlook:

  1. In the Change Account window, click More Settings in the bottom-right corner.
  2. Select the Advanced tab, where we’ll find the Server Timeouts slider.
  3. Increase the slider value to allow for more time before Outlook disconnects.

Keep in mind that setting the timeout value too high may lead to delays in sending emails. However, increasing it slightly can help prevent duplicates caused by timeouts.

After making these adjustments, click OK to save our changes, followed by Next and Finish to close the Change Account window.

By checking and adjusting our mail server settings, we can help ensure smooth communication between Outlook and our email provider’s server, reducing the likelihood of duplicate emails being sent.

Analyzing Email Send/Receive Intervals

When it comes to Outlook sending duplicate emails, one possible cause could be the send/receive interval settings.

By default, the send/receive interval time in Outlook is relatively short, usually set to check for new messages every 30 minutes. This frequent checking can sometimes lead to duplicate emails being sent unintentionally.

To analyze and potentially fix this issue, we can try adjusting the send/receive interval time to a longer duration. To do this, follow these steps:

  1. In Outlook, go to the File tab and select Options.
  2. In the Outlook Options window, click on Advanced in the pane on the left.
  3. Scroll down to the Send and Receive section.
  4. Look for the option labeled “Send/Receive every _ minutes” and change the value to a higher number, such as 60 minutes.
  5. Click OK to save the changes.

By increasing the send/receive interval time, we give Outlook more time to process and synchronize emails, reducing the chances of duplicate emails being sent.

However, keep in mind that this change may also increase the time it takes for new messages to appear in your inbox.

Balancing the send/receive interval with your need for timely message delivery is essential.

It’s worth noting that if you’re using an IMAP email account with Outlook, duplications can also occur due to the way IMAP handles the synchronization of sent items between the email server and the Sent Items folder in Outlook.

If adjusting the send/receive interval doesn’t resolve the issue, consider looking into other solutions, such as configuring your antivirus software to not interfere with Outlook, as mentioned in the Tweak Your Biz article.

The Impact of Internet Connection on Outlook

A stable internet connection is crucial for the smooth functioning of Outlook, especially when sending emails.

It is essential to understand how various factors related to your internet connection play a role in this process.

One primary aspect to consider is the type of internet connection you are using. We recommend using a reliable Wi-Fi or wired Ethernet connection to ensure that your Outlook emails are sent without any duplication issues.

A weak or intermittent connection is more likely to result in duplicated emails, as your device may attempt to resend the message multiple times due to connectivity problems.

Your modem, hub, or router is another essential factor to consider when troubleshooting Outlook’s duplicate email issues.

These devices are responsible for managing your internet connection, and any problem with them may negatively impact your Outlook experience.

Ensure that your modem, hub, or router is up-to-date and correctly configured to work with your specific internet service provider (ISP) settings.

Regularly checking for firmware updates and performing a power cycle can also help maintain optimal performance.

In some cases, network congestion or traffic can affect Outlook’s ability to send emails efficiently.

If you notice that you are experiencing duplicate email issues during peak hours when multiple users are connected to the same network, the increased demand for bandwidth may be causing problems with your email transmission.

In such situations, try to minimize the use of bandwidth-intensive activities such as streaming or large file downloads to improve overall network stability.

In conclusion, monitoring and managing your internet connection is crucial to ensure that Outlook functions efficiently without sending duplicate emails.

By paying attention to various factors such as the type of connection in use, the performance of your modem, hub, or router, and proper network utilization, you can significantly reduce the risk of experiencing duplicate email issues in Outlook.

Exploring the Role of Multiple Devices

One of the reasons why Outlook might be sending duplicate emails is the synchronization of the account across multiple devices.

When our Outlook account is set up on various devices like desktops, laptops, tablets, and mobile phones, it can sometimes lead to the creation of duplicate emails.

As we receive or send emails, these devices try to maintain the most up-to-date information by syncing with the email server.

When synchronization happens simultaneously on multiple devices, it can cause hiccups, resulting in the generation of duplicate emails in our Outlook inbox.

This is especially true for IMAP email accounts, which usually synchronize the entire mailbox with the email server.

To tackle this issue, we can consider reducing the number of devices our Outlook account is synchronized with or adjusting the synchronization settings.

On each device, we can ensure that the Outlook settings are configured correctly, like turning off saving sent items in an IMAP email account.

This can be done by following the steps provided in this Microsoft support article.

Moreover, we should keep our software and devices updated to ensure that they are running the latest version of the Outlook application, minimizing potential bugs and compatibility issues.

Consistent updates can help maintain smooth synchronization and reduce the chances of duplicate emails being created.

In conclusion, the role of multiple devices should not be overlooked when diagnosing the issue of duplicate emails in Outlook.

Proper configuration, synchronization settings, and software updates can help us manage our Outlook account seamlessly across various devices and prevent duplicate emails from cluttering our inboxes.

Potential Interference from Antivirus and Add-ins

In some cases, Outlook might send duplicate emails due to interference from antivirus software or add-ins.

We’ll discuss both of these potential issues and how to resolve them in the following paragraphs.

Antivirus software is designed to protect your computer and email from malware and other threats.

Sometimes, it might cause issues with Outlook sending multiple emails. To check if your antivirus is causing the problem, you can temporarily disable it.

Remember that disabling your antivirus may expose your computer to security risks, so make sure to re-enable it after testing.

On the other hand, add-ins can extend Outlook’s functionality and make it more powerful.

However, some add-ins might conflict with Outlook’s operations, leading to issues like sending duplicate emails.

To troubleshoot this, you can try running Outlook in safe mode. This mode disables all add-ins, allowing you to identify if they’re causing your problem.

If your issue persists even after disabling your antivirus and running Outlook in safe mode, you might have to repair your IMAP account connection.

This can be done by removing and re-adding the email account in Outlook. Doing so updates the settings and ensures they are correctly applied in the application.

Keep in mind that while troubleshooting potential interferences, it’s essential to maintain a balance between your system’s security, functionality, and the need to avoid sending duplicate emails.

Always re-enable any disabled features once you’ve determined whether they’re the cause of the issue or not.

How to Remove Duplicate Emails in Outlook

We understand that dealing with duplicate emails in Outlook can be frustrating and time-consuming.

In this section, we’ll provide you with a few simple steps to remove duplicate emails and help you maintain a clutter-free mailbox.

Firstly, it is essential to identify the cause of the duplicate emails.

You may encounter this issue if you have incorrectly configured rules in your account if your antivirus is interfering with Outlook, or if your OST file has some errors.

Be sure to check these factors before proceeding.

To remove duplicate emails in Outlook, follow these steps:

  1. Open Outlook and navigate to the Mail tab at the bottom left corner of the window.
  2. Select the folder in which you have duplicate emails, such as your Inbox.
  3. Click on the View tab, and turn off the reading pane by selecting Off in the Reading Pane options.
  4. Click on View Setting to open it, and then press the Sort button in the dialogue.
  5. Choose options in the dialogue to set limitations based on your preference and click OK.
  6. Hold the Ctrl key while selecting the duplicate emails, and press the Delete key to remove them from your mailbox.

Remember, regularly checking your Outlook rules and updating your mailbox settings can help prevent the recurrence of duplicate emails in the future.

Additionally, it’s crucial to keep your antivirus software and Outlook properly configured to avoid any interference that might cause the duplication issue.

Following these steps should help you to efficiently and confidently remove duplicate emails in Outlook, keeping your mailbox organized and making it easier to find what you’re looking for.

Enable/Disable Duplicate Sent Items For IMAP Account In Outlook?

Here is the step-by-step guide to enable/disable save copies in the send box.

  • Open Outlook >> Click File >> info >> Account setting >> Manage Profile
duplicate emails in outlook
  • Mail setup dialog box appears to click the “mail accounts”.
outlook sending duplicate emails exchange
  • Account Settings dialog box,
  1. Go to the E-mail tab.
  2. Select the IMAP account so that you will prevent duplicate sent emails.
  3. Click the Change button.
duplicate emails in outlook 2020
  • The Next step is to click the More Settings button at the bottom-right corner of the “POP and IMAP account settings” dialog box.
sending duplicate emails
  • Please go to the Advanced tab in the Internet Email setting, check the option ‘Do not save copies of sent items in the Sent Items section, and click the OK button.
Do not save copies of sent items
  • The above steps bring you back to the change account box, click next to finalize the setup.

The above tutorial gives all your answer to the question of how to prevent and remove Outlook duplicates.


While technology has undoubtedly simplified our lives in countless ways, it’s not without its occasional hiccups, as seen with the duplicate emails issue in Outlook.

Yet, as with most tech-related challenges, understanding the root cause is half the battle. Now that we’ve explored the various reasons behind Outlook sending duplicate emails and how to address them, you’re better equipped to handle such glitches in the future.

Remember, software will always have its quirks. The key lies in staying informed, being proactive in addressing known issues, and always seeking out knowledge.

As Outlook continues to evolve, it’s our hope that such challenges become rarer. Until then, keep this guide handy and ensure your communication remains seamless and duplicate-free.

Thank you for joining us on this exploration of one of Outlook’s most puzzling behaviors. May your inbox be ever efficient, and your sent folder free of unwarranted replicas!

Also Read:

Amit Bansal

Hello, my name is Amit Kumar Bansal, and I am the founder of MailSmartly.com. Through this blog, I focus on Microsoft Outlook, offering insightful and informative content. Additionally, I produce educational videos on YouTube to further enhance the understanding of my audience. visit my YouTube Channel

View all posts

Leave a Comment