Automatically remove duplicate mails in Thunderbird

Martin Brinkmann
May 18, 2007
Updated • Mar 16, 2014
Email, Thunderbird
|
19

It happens sometimes that you find duplicate mails in your inbox in Thunderbird. This can happen for instance when you retrieve new emails from the mail server and get disconnected during that process.

It can happen then that those emails will be retrieved again when you check for mails so that you end up with them being listed twice in the email client.

That's obviously not what you want, and while you can deal with the issue by deleting all duplicate emails manually, it may take some time to do so depending on the number of mails you have received.

Thunderbird has a nice hidden feature that defines how to treat duplicate mails.

I'm going to show you how to set it correctly so that duplicate mails are removed automatically.

Remove dupes in Thunderbird automatically

You have to click on Tools > Options to open the preferences in Thunderbird. Click on the Advanced tab there and select Config Editor under Advanced Configuration. Note that you may receive a warning message when you open the editor for the first time. You need to accept the warning before you can continue.

If you are using the Firefox web browser you may notice that it looks identical to the one you find in the browser. Enter mail.server.default.dup_action in the filter and the entry should be shown alone in the main window.

thunderbird remove duplicate emails

Now right-click that entry and select modify from the menu. You can change the parameter to the following values:

  • 0 - this is the default value. It retrieves duplicate mails like normal mails.
  • 1 - if you set the value to 1 duplicate mails will be deleted automatically once retrieved
  • 2 - if you set the value to 2 duplicated mails will be moved right into the trash
  • 3 - the value 3 finally marks duplicate mails as read

If you want to delete duplicate mails automatically in Thunderbird you set the value 1.

Closing Words

You may want to experiment with those options for some time before you select a final value for it. While deleting duplicates may sound like the best option right out of the box, you may want to be sure that no regular mail gets caught in the cross fire. While unlikely, it is better to be safe than sorry. My advise is to use a value of 2 or 3 instead and monitor this for a while before you set the value to 1.

Summary
Remove duplicate emails from Thunderbird automatically
Article Name
Remove duplicate emails from Thunderbird automatically
Description
Explains how to configure the Thunderbird email client so that it removes duplicate emails automatically.
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Comments

  1. JMGG said on January 19, 2012 at 8:25 am
    Reply

    You said that Outlook isn’t your main email client, so which is your main one?

    1. BalaC said on January 19, 2012 at 9:42 am
      Reply

      I think its thunderbird

    2. Martin Brinkmann said on January 19, 2012 at 10:15 am
      Reply

      It is Mozilla Thunderbird.

  2. Salaam said on September 24, 2012 at 9:52 pm
    Reply

    Awesome! This actually solved my problem… what a stupid bug.

  3. Claud said on December 19, 2012 at 2:08 am
    Reply

    If this is the same bug that I’ve encountered, there may be another fix: (1) hover over open Outlook item in Taskbar, cursor up to hover over Outlook window item, and right-click; (2) this should give you Restore / Move / Size / Minimize / Maximize — choose Move or Size; (3) use your cursor keys, going arbitrarily N/S/E/W, to try to move or size the Outlook window back into view. Basically, the app behaves as though it were open in a 0x0 window, or at a location that’s offscreen, and this will frequently work to resize and/or move the window. Don’t forget to close while resized/moved, so that Outlook remembers the size/position for next time.

    1. Lynda said on February 12, 2013 at 3:37 pm
      Reply

      THANK YOU Claude!!! I could get the main window to launch but could not get any other message window to show on the desktop. You are my hero!!!!

    2. Chad said on November 20, 2018 at 4:24 pm
      Reply

      Solved my issue! 6 years later and this is still problem…

    3. Ivan X said on January 21, 2021 at 4:50 pm
      Reply

      Fantastic. Thank you. Size did the trick.

  4. Andrew said on October 26, 2013 at 7:06 am
    Reply

    This solved my Outlook problem, too. Thank you. :)

  5. Charles said on December 7, 2013 at 7:23 pm
    Reply

    Thank you so much, this started happening to me today and was causing big problems. You are a life saver, I hope I can help you in some way some day.

  6. garth said on November 7, 2014 at 7:13 pm
    Reply

    You are a god – thank you!

  7. Faisal said on February 9, 2015 at 10:09 am
    Reply

    thanks a lot…. work like charm.. :-)

  8. Simon said on March 24, 2015 at 11:36 pm
    Reply

    Yah…thanks Claude. I’ve been having the same problem and tried all the suggestions…your solution was the answer. It had resized itself to a 0/0 box. Cheers

  9. Olu said on April 14, 2015 at 1:35 pm
    Reply

    Excellent post. This had me baffled even trying to accurately describe the problem. This fixed it for me.
    Thank you

  10. Coenig said on July 23, 2015 at 7:36 am
    Reply

    Thanks a lot for the article. Don’t know why it happenend, don’t know how it got fixed, but it was really annoying and now it works :-)

  11. Fali said on January 20, 2016 at 4:19 pm
    Reply

    Thanks a lot. I was facing this issue from past 3 week. I tried everything but no resolution. The issue was happening intermittently and mainly when I was changing the display of screen ( as i use 2 monitors). The only option i had was to do system restore. But thanks to you.

    1. MIki said on January 10, 2019 at 11:54 am
      Reply

      I’ve been tried to sole this problem for 12hours. Your comment about changing the display of screen helped me a lot!! Thanks!!

  12. Christina said on January 20, 2016 at 6:14 pm
    Reply

    Thank you…don’t know why this happened but your instructions helped me fix it. Running Windows 10 and office pro 2007

  13. Oz said on July 22, 2016 at 3:20 pm
    Reply

    Great tip! Thanks!

  14. Tracy said on September 1, 2016 at 4:48 pm
    Reply

    Worked for me, too – thank you!!!

  15. shawn said on September 9, 2016 at 10:25 am
    Reply

    It’s Worked for me, too
    thank you very much!

  16. Jari said on October 31, 2016 at 11:53 am
    Reply

    I had a similar issue with Outlook 2013 on Windows 10 and this helped me to fix it. Thank you very much!

  17. Michel H said on November 30, 2016 at 11:08 pm
    Reply

    Thank you so much. Solved!
    Considering you published this in 2012, incredible not been debugged by Microsoft.
    Thank you again. M

  18. Ziad Bitar said on January 9, 2017 at 2:00 am
    Reply

    This problem was faced by only one user logging to TS 2008 r2 using outlook 2010.The issue was resolved.

    Thanks.

  19. Anonymous said on February 15, 2017 at 5:24 pm
    Reply

    Great tip. Thank you!!!! If it helps, I had to use the Control Key and the arrow keys at the same time to bring my window back into view. Worked like a charm.

  20. Rochelle said on March 6, 2017 at 11:59 am
    Reply

    Thank you, this worked !!!!

  21. anom1234 said on May 20, 2018 at 11:20 pm
    Reply

    Man, you are a fucking god. Thanks a lot, what an annoying bug!!

  22. JC said on October 12, 2020 at 2:14 pm
    Reply

    Awesome, this post solved the issue. Many thanks!

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