How to remove duplicate emails in Outlook 2016 and 2013 quickly and safely

From this article you will learn why multiple copies of the same message may appear, and how to find & remove duplicate emails in Outlook quickly and safely, ensuring that all of your important messages remain intact.

If you've been using Outlook for a while and have only a few dozen or even a few hundred messages in your inbox or archive folders, then you're most likely to have never faced the problem of duplicate emails and this will hardly happen to you in the near future. Lucky you are! : )

But to be honest, I've never met a person like that. It's estimated that an average Outlook user receives around 50 - 100 messages a day. So, usually we have thousands and thousands of emails stuck in various folders and you may not even have a vague idea of how many duplicated emails actually are in your Outlook.

The reasons why duplicate emails appear in Outlook

Duplicate emails in OutlookThere are plenty of causes why duplicate email messages may occur in Outlook. For example, you can receive multiples copies of the same email from your friends or teammates who forward to your attention the same newsletter, press release or an exciting news item, which is often the case in our company.

Other reasons are more technical and not so obvious. An interrupted or incorrect synchronization with a laptop or mobile device is one of the most frequent causes, e.g. if you read some messages on the phone and others on your PC, and then place the read messages to a different folder on each device.

Sometimes duplicate e-mails are produced by a hiccup of the mail server, especially if you activated the "Leave Messages on the Server" settings option. Incorrectly configured Outlook rules when two or more "move a copy to" rules apply to a certain incoming message also lead to email duplication. Merging several PST files into one may result in duplicated messages too.

And even your antivirus software may create duplicate e-mails. Of course, it won't do this deliberately, it might be just an intermittent side-effect, especially if you click the "Send/Receive" button all too often interfering in the scheduled send/receive/store process.

Whatever the reason is, multiple copies of the same message might cause great confusion and disorder in your Outlook, making your work more stressful and less productive.

Problems created by duplicate email messages

As you probably know, Outlook is one of the most complex and resource-hungry applications of the Microsoft Office suite. It requires quite a lot of resources for smooth performance, and the more email items you have, the more memory, disk space and CPU usage it consumes. Finally, it may reach the point when the existing resources do not suffice and your Outlook will start to slow down in performance. For example, you want to find a particular message using Outlook's Instant Search, but all that you see is "Searching…". And you have to wait patiently while Outlook iterates through all email messages in a given folder including duplicated ones.

On an average PC, Outlook starts to slow down when the mailbox reaches 2-3 GB, and if you don't reduce the size of your mailbox and Outlook data file (.pst), your Outlook may start hanging, freezing and not responding.

How to delete duplicate emails in Outlook

Unfortunately, even the latest version of Outlook 2013 does not provide any tool that would let us remove duplicate email messages in Outlook folders. Microsoft suggests a way, or rather a workaround, to delete duplicates manually. You can try it if you have time, and this may even work if you have a few dozen emails. This might be challenging if you have several hundred messages, and next to impossible if you have thousands… and absolutely impossible if those thousands are stored in different folders.

So, how can you eliminate all duplicated emails from Outlook? There exist a number of different tools to eliminate dupes. Some of them are quick, simple and free. Others are more flexible and sophisticated but, as you may guess, paid. We will cover pros and cons of both types and you will decide which is right for you.

A free tool to remove duplicates in Outlook folders

The most popular and time-tested free tool is Outlook Duplicate Items Remover, also known by the abbreviated name ODIR (you can download it here).


The biggest advantage of this tool, apart from being free, is that it's very straightforward and easy to use. This is how the main window of ODIR looks like:
Outlook Duplicate Items Remover add-in

As you see, all you need to do is choose a folder to check for duplicates and click the "Remove duplicate items" button. Besides mail, this tool can search for duplicated contacts, tasks, notes and calendar items.

The ODIR add-in does not actually delete duplicate emails or other items that it finds, it lets you judge whether these are real duplicates. The plug-in creates a special "ODIR_Duplicate_Files" subfolder in the selected folder and moves the found duplicates into it, and this is also good and safe for us, Outlook users. If you don't have any messages of importance in the selected folder, then you can simply delete the contents of the ODIR_Duplicate_Files folder. Otherwise, you can compress or zip this folder and move it your hard drive or a flash drive before deleting the duplicate messages, just to be on the safe side. : )


If to speak about shortcomings of this plugin, the main drawback is the lack of flexibility, i.e. lack of settings that would let you configure the search criteria. This add-in can look for duplicates within one Outlook folder only and cannot even search in subfolders of the same folder. So, if you are an organized person and have a multi-level structure of folders and you want to search for duplicates across all the folders, the ODIR add-in will be of very little help.

How ODIR finds duplicates

If you are a technical geek or guru, you might want to know what criteria the ODIR add-in uses to recognize an email message as a duplicate. The add-ins checks the following properties of mail items and if all of them match, the email is considered a duplicate:

  • Received emails - the internet message ID
  • Sent emails - email subject and the time the email is sent
  • Unsent emails - email subject only

While the first two (received and sent emails) do not raise any questions, you'd probably better not use this add-in to remove duplicates from the Drafts folder. If you actively use drafts in Outlook, for example to compose several versions of your reply when responding to a very important message, the ODIR add-in will recognize them as duplicates even if they have the same subject but different text in the message body.

Flexible, fast and safe way to remove duplicate emails

Regrettably, there is no free tool that would meet all the criteria in the heading, i.e. be flexible, reliable and quick. If you are looking for this kind of tool, check out Duplicate Email Remover, a time-tested solution from a trusted manufacturer of Outlook plug-ins (MAPILab) that has been working in this industry for many years.

This add-in provides a handful of advanced options, which are not available in free tools and which let you search for duplicates in the folders you specify, with the priority you set, and based on the criteria you choose.

Search for duplicate emails in several folders with specified priority

With Duplicate Email Remover you can choose the folders you'd like to check for duplicates and, most importantly, you can set the priority of folders.
Choose the folders to look for duplicates and set the priority.

As you see in the screenshot above, you choose the folders to scan for duplicates on the left pane and set their priority on the right pane using the up and down arrows.

If multiple copies of a particular message are present in all the folders you've chosen, the Duplicate Email Remover will leave only one message in the folder that comes first in the list (the Notification folder in our case) and remove duplicate e-mails from the other folders. If identical messages exist only in the 2nd and 3rd folders, the message will be left in the 2nd folder and deleted from the 3rd, and so on. A very handy option, isn't it?

Choose what to do with duplicate emails

Another useful feature of the Duplicate Email Remover plugin is the ability to choose the action to be performed with duplicate e-mails. You can opt to delete them permanently, or move to the Deleted folder, mark with flag or mark as expired, copy or move to a specified folder.
Choose the action to perform with duplicate emails.

Apart from choosing the action, you can also specify the time period, i.e. apply the chosen action to email messages received within the last few days, weeks, months, or anytime.

Define which message fields to compare

This is also a very useful option if your aim is to find duplicated messages with tiny differences, e.g. the sender name or date and time of sending. With Duplicate Email Remover you can handle these almost identical emails too.

You simply choose the fields by which you want to compare mail items in a certain folder or folders, and then delete duplicate messages. For example, if you often receive multiple copies of the same message from the same person(s), uncheck a few irrelevant fields so that only one such email will remain in your inbox and all duplicates are gone.

Define which message fields to compare for duplicates.

As you see in the screenshot above, three fields are predefined and cannot be unchecked. These are the main fields by which the Duplicate Remover detects duplicates: message body, subject and sender's email address. The others are up to you.

Well, if you are interested to try Duplicate Email Remover, you can download an evaluation version here. This tools works with Outlook 2016, 2013, 2010, 2007, and 2003.


Besides the two add-ins we've just discussed, there are tens of other duplicates remover tools, paid and free. If you have time and the desire to experiment, you can look through this catalog. You can get a much bigger list by searching in google, bing, or any other search engine.

And finally, a little piece of advice, if you let me. When choosing the duplicate remover tool, make sure it is from a reliable and trustworthy vendor that has been on the market at least for a few years, Microsoft Partners and MVPs are given preference. You don't want some twopenny-halfpenny hack to bring havoc to your Outlook and eliminate a couple of important emails, do you?

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Category: Outlook Tips

Table of contents

62 responses to "How to remove duplicate emails in Outlook 2016 and 2013 quickly and safely"

  1. Petrick Nayasa says:

    Informative article!! Added to this due to various reasons Outlook create replica of same email. But the problem can be sort out by Two ways:

    * Keep option in Outlook saying " Leave copy of message on server" disable. This would prevent downloading of same email twice.
    * Set of Rules in Outlook should be properly manage properly otherwise it would generate duplicate emails in Outlook.

    Already having duplicate emails in Outlook. Do not Fret out Use SysTools Email Duplicate Analyzer to remove repeated emails in batch across PST files.

    • dont do it says:

      it will also remove emails from the server and store them with in your local PST . doing so means if the computer fails (hard drive) then you have no lost ALL of your email.

      • BT7474 says:

        I agree - This is why I always send an email that I send to somebody to myself also by placing my email into Bcc box also because if there is a fault a copy of my emails will also be saved on Virgin Media's Computer server also - It is easier to ask Virgin Media Technical Department to install my various accounts again and download my emails, especially after having to reinstall Microsoft's Operating System than to search for all the various emails' .pst files.

  2. Shashikant says:

    Many Thanks, Your solution to remove duplicate emails is as pretty and beautiful as you.

  3. Lenny Burns says:

    There is a way to do this without a tool and without worrying about folder structure.

    Export your email to a PST.
    Then manually delete the contents of those folders, and you can delete the sub-folders too, because they are in the backup.

    Then, re-import the PST, checking the box that say "Do not import duplicates" (or something very similarly worded.)

    Once complete, you have NO dupes, AND a backup of your email to use in the future.

  4. Hi Lenny,

    This seems to be a very easy way indeed! I can see only one shortcoming. If you have some folder that contains very important emails or emails to follow up, and there are duplicates of those emails in other folders, the first found occurrence of an email will be left and all copies deleted. This means that a copy of the email may be deleted from the "Very important" or "Follow-up" folder.

    Thank you for your comment!

  5. MarksPaul says:

    If you want to remove duplicate emails in Outlook 2010 and 2013, then you can take help of third party Kernel for Outlook Duplicates Remover tool which can quickly and safely remove all items of MS Outlook mailbox.

  6. marry says:

    This is an informative post regarding the reason behind duplicate mails and solution to remove that. There are two common ways that can be followed to remove the duplicate mails from Outlook, which are –

    Manual method
    Automatic method

    Automatic method is more effective because it guarantees complete and effective removal of duplicate mails.

  7. TheAncient says:

    Apparently a method of removing duplicates IS a built right into Outlook.
    To access this feature select Outlook mail folder, go to Home tab > Delete section > Delete > Clean Up
    More details at

  8. tasks. If I h Matievich says:

    This all fine, and I see that the problem has been going on for some time, but my problem is not duplicate emails; it's duplicate (or rather triplicate taske. If I delete even one of them, they all disappear.

    If this has been going on for so many years, why hasn't Microsoft fixe it yet???

    At any rate, any help with triplicate task?


  9. Herb says:

    Thank you for this article Svetlana, it was exactly what I was looking for!

  10. Sean says:

    As far as I know ODIR does not work in Outlook 2013. Am I missing something?

  11. Pete says:

    Does anyone know of a duplicate email remover which works with Windows (7) Live Mail - and can search in multiple email sub-folders (below Inbox)?

  12. Jean-Michel says:

    Hi, I'm using Outlook on my MacBook Air with Maverick OS.
    Do you know if there are tools I can use to remove duplicated emails with this configuration?
    Thanks a lot!

  13. tc says:

    can this work to remove duplicate contacts, or even contact that are already under delete items?

  14. Oliver says:


    Another free solution (and also doable for Mac users) is to use thunderbird and install the "remove duplicate emails (alternative)" plugin.
    It does a fabulous job.

    The only drawback is that you will have to re-download all your emails first into Thunderbird, before you can de-duplicate your mails. You can delete that thunderbird email account after de-duplication, however, which wiki give you all your drive space back.

  15. Santosh says:

    I like the article very much, it is self explanatory as well as very simple language used.
    Thanks for sharing.

  16. Ben Che says:

    Does ODIR support Outlook 2010 Professional Plus on 64bits Windows 7 ?

  17. Ben Che says:

    How can I know the version of Outlook 32bit or 64bit ?

  18. Ron says:

    Your article caught my attention and I downloaded the program ODIR. It installed without any problems and I can see the Add-Ins tab on the Outlook menu. When I select the tab and click on ODIR option and click on the dropdown list Remove duplicate items list... I get the following error message; "ODIR was unable to read your pst or ost file. Removing duplicate items is not possible."

    Is there anything I need to do to enable it to read the pst file? I am using Outlook 2010 and odir is something I have been looking for for quite some time. I would love to give it a try.

    Thank you very much.

  19. Abizar says:

    Thank you :)

  20. Nick says:

    Hi Svet,

    I'm using ODIR but my outlook file is already very large. Its about 19GB, and this often causes the ODIR to hang. Is there a better way to remove duplicates in such large files? I know I should have done it earlier ... but that didnt happen.

  21. keving says:

    I highly suggest DublicateFilesDeleter!It's a very usefull tool!

  22. Pat2014 says:

    Was struggeling with duplicate mails in Outlook 2007 for a long time. Since I only had that problem with 2 accounts from the same provider and not with another account from another provider, the problem had to lay there. So I removed my accounts from the first provider. After I reconfigured my accounts manually, the problem was solved. But instead of duplicating an account after I reconfigured the first account to save me some time with the second account, I manually configured the second account from the same provider as if it was a new account. So duplicating an account to easily duplicate the settings and then changing only the e-mailaddress and e-mail name, made Outlook 2007 believe that these were in fact not seperate e-mailaddresses but a duplicate e-mailaddress, even though I changed the e-mailaddress.

  23. chris cooper says:

    This free one is quite good and works with 2013:

  24. Han So-Low says:


    Please update your article. It states that this works with Outlook 2013 while the developer of ODIR clearly states that it is NOT compatible with Outlook 2013.


    • Hello Han So-Low,

      You are absolutely right. And I have the following notice under ODIR' cons:
      "One more serious limitation is that the Outlook Duplicate Items Remover does not support Outlook 2013 and Outlook 2010 64-bit yet."

      The other solution discussed in the article, Duplicate Email Remover, works with all Outlook versions, including Outlook 2013.

    • BT7474 says:

      I know what is the computer technical difference between; 32-bit and 64-bit - Therefore, the way I interpret it was that it didn't work for 64-bit operating systems. - It is possible to make 32-bit compatible with 64-bit but difficult to make 64-bit backwards compatible with 32-bit. - for example, if you had a vehicle with 32 people it is easy to fit them into a vehicle that holds 64 people but to fit 64 people in a vehicle with only 32 seats is more difficult.

      • BT7474 says:

        I forgot to say that the program was written to work with 32-bit and NOT 64-bit - It would have to be rewritten to work with 64-bit version because of the way it was written. - Some applications are written to work with BOTH 32-bit and 64-bit but this one was only written to be compatible with 32-bit.

  25. kaustubh says:

    Amazing Tool ! Cheers!

  26. supadupa says:

    Does anybody know any tool that would AUTOMATE this? What I have seen so far, I think all of these tools still require manual work, even if it is just a couple of clicks.

    I want the duplicates to be moved to a spesific folder or deleted automatically, preferably every time I open outlook.


    • Alexander says:


      It is a specific task. You’d better address this question to developers of the plug-ins for removing duplicates.
      There is more than a dozen of such add-ins, we’ve described only the most popular ones. Perhaps, you will find such an option in one of those add-ins.

    • BT7474 says:

      I don't think that there is one - It could have been worst. - The other PC's duplication applications (find duplications in any folders not just email folders) usually you have to manually decide which ones to keep and select which ones to delete - I think it is a security problem. - It isn't that simple to select an identical file (even though it looks simple), for example, group by; number of characters, dates, file names, and memory size, are just some things which make it complicated, which then raises the questions if I have to manually select virtually everything then what is the purpose of most duplications' applications?

  27. Dilshad khan says:

    hi I am using outlook and we have received to multiple duplicate so I want to delete duplicate mai so kindly sujest me..

  28. pravin kumar says:

    Thank you 4 Ur article on Outlook duplicate email remover..
    Me need a support in free to remove all my outlook duplicate emails..
    How can i do it..
    Hope U reply me soon..
    Hv nice time n enjoy Ur life..
    Thank you once again..

  29. Shane says:

    As already stated, use 'Clean Up' button in 'Delete' section of toolbar. It comes built in and I've used it to remove duplicates.

    • Rexter says:

      I recently discovered the "Clean Up" feature in Outlook 2013 but it leaves 1000s of duplicated messages and I don't see any settings to change it to do any better so I would say to try it since it's built in and look at the results and go from there. In one folder it wouldn't delete any duplicate messages that had attachments.

  30. khoshal says:

    thanks for doing the article.

  31. Tina Rodrigo says:

    Thank you very much. And if somebody want to delete duplicate file or simply find them then I recommend Dulpicate files deleter,it is very simple to use. But make it sure to keep the important files in back up. It is off topic but it will certainly help the people.

  32. Kevin Brown says:

    You have some Duplicate Files on your computer which hampers your memory space.
    Just use "DuplicateFilesDeleter".If you use this software you will be get comfortable.

  33. taras says:

    You should definitely try the Duplicate Files Deleter program

  34. Atul Garg says:

    I tried that cleanup method available in outlook. It has options in setting. It clearly states that it will remove the duplicate items. There is also a way to select current folder only or folder and sub-folders. Very pleasant to see all this. But it does not remove any duplicate items. It does remove a number of important items from all folders but none of them are duplicates. I analysed a lot but the program behavior appears to be random.

  35. Mathyria says:

    Dear Svetlana Cheusheva
    would you please introduce the operation in outlook2016?
    I download and install ODIR, but can not found the button or in COM.
    thanks in advance.

  36. Vampire says:

    Title to delete duplicate emails but in "Problems created by duplicate email messages" then delete duplicate Contacts. For ordinary users, it is necessary to fix it basically without necessarily using the 3rd software to intervene.

  37. Kenneth says:

    How do I run Outlook Duplicate Items Remover?

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