Stop and remove duplicate email messages in Outlook 2016 and 2019

Applies to: Office 2019, 2016, 365. Windows 7, 8, 10 and macOS (with small adjustments).

Have you ever got a bunch of redundant duplicated email items, contact persons and calendar entries in Outlook and wanted to quickly clean up these annoying duplicates so you can focus on the real stuff?

If so, keep reading, because today we’ll show you how to you can stop receiving those messages and remove duplicated email from your mailbox without purchasing a costly remover tool.

We’ll first explain the most prevalent reasons for the most common email duplication cases. We’ll then provide some simple solutions that you can easily implement to cleanup redundant conversations, contacts and meetings from your email inbox with ease.

Reasons for duplicate email in your mailbox

From what i have seen in the past, Outlook duplicates typically origin from six main reasons:

  1. Rules not configured correctly: There might be cases that two or more rules are fired upon receiving email, resulting in multiple instances of the same messages.
  2. Incorrect account setup: In several cases, i have seen that users mistakenly defined multiple occurrences of the same email account  and this results in multiple instances of each incoming email, contacts and calendar entries.
  3. Send / receive interval are too short. If the frequency of your inbox update is too short; Outlook might load the message into your inbox, BUT might not be able to mark messages occurrences as synchronized/loaded. This results in multiplied occurrences of the same messages.
  4. Synchronization issues: We have also observed duplicated contacts and messages resulting from sync problems with 3rd party providers.
  5. User errors while manually copying and pasting meetings and appointments in the Outlook Calendar.
  6. Incorrect merging of several Outlook personal folders (also referred as PST files) into one folder.

Impact of duplicated Outlook items

  1. They harm your productivity.
  2. They confuse and cause errors. Just imagine replying more than once to the same note :-(…
  3. They might impact your Outlook client loading performance. The more messages stored on your computer or server Outlook will need to load on startup, the slower its performance will be.
  4. Dups fill up your inbox. Business users will need to delete email to to comply with the allocated email storage capacity provided by their IT department.

Now that we understand the root causes and impact, let’s focus on some possible solutions.

Remove duplicate email in Outlook

There are several email duplication removing utilities and add-ins in the market, but we do believe and recommend that you use the out of the box Outlook functionality. Read on for the complete procedure.

  • Open Microsoft Outlook (this process will work in versions 2013 and 2016).
  • It’s always advisable to backup your email before executing a clean up procedure. Here’s a step by step procedure to export and backup your Outlook email, calendar and contacts.
  • After you are done, select the folder in which the duplicate emails are.
  • Under Home, go ahead and select the Clean up drop down box in the Ribbon.
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  • Select Clean up conversation to delete and move duplicate emails in the conversation to the Deleted Items folder.
  • Clean up folder will delete and move duplicate emails in the specific folder to the Deleted Items.
  • Clean up folder and sub folders will allow you to clean up also subfolders.
  • Once done, you might right click on the Deleted Items folder and hit Empty Folder to delete your duplicated email instances for good.
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Note: If you are a Microsoft Office for MAC user, you will find the Clean Up option in your Home Ribbon.

Preventing Email duplication issues

  1. If relevant, check on your Outlook rules to ensure that multiple rules are not firing in parallel for each incoming message.
  2. If using 3rd party web email providers, Check that your  GMail, Yahoo and accounts are correctly defined in Outlook.
  3. Now, increase the frequency of your inbox update. Here’s the step by step process:
    • In Outlook, hit Send / Receive
    • Hit Send / Receive Groups
    • Now go ahead and select Define Send / Receive Groups
    • Now set the time interval to a value between 15 and 30 minutes (See screenshot below)
    • Click OK.


Cleaning up duplicated contacts

If you have found duplicated contact people in your People tab, you will find this tutorial very useful to remove the redundant contacts. Follow the outlined steps to merge duplicated entries in your Outlook contact list.

Hope it helps!

9 thoughts on “Stop and remove duplicate email messages in Outlook 2016 and 2019”

  1. Sorry, but it’s not clear to me what is the difference between cleaning up CONVERSATIONS & cleaning up a FOLDER? Both refer to duplicate emails in the folder. Isn’t it the same thing?

  2. The backup tool says it applies to Outlook 2007 and earlier, but your article is for Outlook 2016. Have you tried this tool and procedure on 2016?

  3. Good point. Fixed the link to the latest Microsoft backup procedure for contacts, appointments and messages.


  4. I have tried your recommendations for cleaning up email folders in Outlook 2016. I always get the message that first that “No messages were cleaned up” followed by “Only messages that satisfy your Clean Up Settings will be moved to the “Trash” folder”. No matter what settings I choose no messages are cleaned up. Can you please advice me?

  5. Clean up folder does not remove all duplicates from inbox. Is there another utility that does. I am getting emails in 4-to-6 duplicates at a time. At best the clean up function removes 2 duplicates.

  6. no clean up ‘button’ in outlook 2016 for Mac when you go to home ..anywhere else .I have 900 sent duplicate emails ..thru in my outlook ( I disconnected in Tools /accounts/gmailaccount/advanced/folder/sent/don’t store a copy of sent messages so it stopped the duplicated emails ( I only get one gmail sent mail) but I still have to erase the 900 emails who I had previously before this manipulation. my outlook is outlook for Mac version 16.16.3 ( I have a MacBook Pro) (outlook is 2016) my Mac is MacOs high Sierra version 10.13.6
    there is no “clean up’ in the home ribbon .Any Help from an outlook for Mac expert would be welcome Thank you very much .jean-pierre

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