Reduce the folder size of Thunderbird to free up disk space

Martin Brinkmann
Feb 4, 2007
Updated • Mar 15, 2014
Email, Thunderbird
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Today when I wanted to install a new program on my version of Windows I noticed that I only had 50 Megabytes of storage left on the partition. This was troubling as I had only Windows installed on the drive and a couple of applications, which certainly should not fill the 10 Gigabyte partition to the brim.

So, I checked for the largest folders and files on the partition and discovered that the Thunderbird email client was using more than 3 Gigabytes of space in the application data folder on that partition.

I only had about 100 mails in the mailbox at that time but the size of the folder itself was listed with 500 Megabytes.

That's a lot of storage for 100 mails. I remembered that Thunderbird did not delete the mails right away even though they had been deleted from the trash or spam folder.

What happens when you delete emails is that they only get flagged but kept in the mailbox until it is compressed.

This was the cause for the discrepancy between the meager amount of mails and their size, and the big huge mail folders on my c: partition.

thunderbird free space compact

The solution nevertheless is pretty easy. All that needs to be done is to compact the folders which removes all deleted mails immediately. I was able to reduce the folder size of my Thunderbird folder from a size of more than three Gigabytes to 300,000 Kilobytes freeing up valuable disk space on my main partition.

Just right-click a folder and select compact this folder to remove all deleted emails and keep only emails that are visible in Thunderbird. You could check the Disk Space option to automatically compact folders if that saves a defined amount of kilobytes (You find the option under the advanced tab under Network & Disk Space in the Thunderbird options).

thunderbird free disk space

Here you can define the threshold in Megabytes that Thunderbird will use to determine whether to compact mail folders or not. Make sure the "compact all folders when it will save over" is checked.

If disk space is low on your computer, reduce the 20 Megabyte value further, for instance to 5 Megabyte. This effectively means that Thunderbird will compact a folder whenever 5 or more Megabyte of data can be freed up by doing so.

Prime candidates for the compact command are the inbox, trash and sent folders of each mailbox that you are using in the email client.

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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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