Outlook 2016 Duplication Bug
It’s come to our attention that the most recent version of Outlook 2016 has a bug if you’re using the POP3 protocol that causes it to download duplicate messages, remove message from the server even if it isn’t supposed to, or both. If you’d like to read about this known issue on the Microsoft site, click here.
If you have this version and are experiencing duplicated email and/or emails being removed from the server before you think they should be (as seen via webmail or mobile devices) you probably have the version with the bug. To verify the exact version of Outlook you’re using. At the top left, click the File tab, then in the left column, click Account. On the right side, there should be a section labeled Product Information. Toward the bottom of that section, click About Outlook. In the About box, there should be a full version number. They say that the one with the bug is version 16.0.6568.2025.
Updating to the fixed version of MS Office
Microsoft says they’ve put out an updated version of the program that fixes this bug. We don’t have first hand experience with the new version, so can’t vouch for the fix. To try the updated version first before the workaround, do the following.
- Open MS Outlook.
- Click File then Account (or Office Account).
- On the right under Product Information, note the version listed under Office Updates.
- If the version is not at least 16.0.6568.2036 or later, click Update Options, then Update Now.
Implementing the work around in case the update above did not work.
If this does not work and you need to try the work around, here’s the procedure.
- First, in Outlook, click the File tab then Account (or Office Account).
- On the right under Product Information, click Update Options, then Disable Updates. If you don’t do this, Office will be updated automatically back to the version with the bug.
- Close all Office programs.
- Open a command prompt. To do this…
– Windows 7 users, click the Start button, and in the search box type command prompt, then click the Command Prompt result.
– Windows 8 and 10 users, go to Search and enter command prompt, then click the Command Prompt result.
- All users, in the command prompt window, type the following lines each followed by the Enter key.
cd C:\Program Files\Common Files\microsoft shared\ClickToRun
officec2rclient.exe /update user updatetoversion=16.0.6366.2068
- When Office finishes updating, open Outlook again.
Cleaning up the duplicate messages.
After Office has been updated or the fix has been implemented, Outlook may download one more round of duplicates. Fortunately in Outlook 2016 there’s an easy way to clean this up.
First you’ll want to backup the Outlook data file. To do this…
- Go to the File tab, then click Account Settings, then the Account Settings flyout.
- On the Account Settings screen, click the Data Files tab.
- Select the file for the account with the duplicates, then above click Open File Location. This will open a Windows Explorer window to the folder where the data file is stored.
- Close Outlook because you can’t copy the data file if it’s open.
- Create a new folder called Backup (or whatever you wish to name it) and Copy–not move–the file to the new folder.
- Once the copy is complete, close the folder window and open Outlook again.
- Select the folder in which the duplicate emails are located, like the Inbox for example.
- On the Home tab’s toolbar, in the Delete section, click Clean Up then outlook-2016-duplication-bug.
- Clean Up Folder And Sub Folders will allow you to clean up the folder you’ve highlighted as well as any sub folders it contains.
- On the small Clean Up Folder window, click Settings.
- On the Settings screen, scroll down to Conversation Clean Up.
- We recommend unchecking all but the first (When cleaning sub folders…) and last (When a reply modifies…) check boxes.
- For “Clean up items will go to this folder:”, click Browse.
- We recommend creating a new folder for the cleaned up items. This will allow you to peruse these items to make sure the clean up was accurate before deleting them. Make sure you create it under the same account as is being cleaned up if you have more than one account.
- When finished here, click OK on the Options screen.
- Now click Clean Up Folder to run the clean up operation. NOTE: This could take a while depending on how much mail you have and how much has been duplicated.
- When clean up is finished, check the folder to which you had duplicated items sent.
- Once you’re satisfied that the clean up operation was accurate, if you want to permanently delete the duplicates, select the folder containing all the duplicate items, hold down the Shift key, and press Delete on your keyboard.
- You should be asked if you want to permanently delete these items. If you’re ready, click Yes (or OK).
- That’s it, you should be done for this folder.
- If you have additional folders with duplicate emails, repeat the procedure.