Fix Slow Or Hanging Thunderbird Email Client

Martin Brinkmann
May 19, 2009
Updated • Jun 29, 2017
Email, Thunderbird

The following guide provides you with instructions on fixing the Thunderbird email client when it becomes slow or hangs regularly.

Thunderbird is a desktop email client that is seen by many as a viable alternative to Microsoft Outlook on the Windows operating system. Users who use the client heavily, may experience slow downs or lags when using the desktop email client after some time.

This can usually be attributed to corrupt msf files in the Thunderbird profile folder. Thunderbird stores the emails in a file without file extension that has the same name as the folder name in the email client, for instance inbox for the inbox folder.

Each of these files contains the emails of the specific folder. Each folder has a msf file associated with it that is an index of all emails stored in that folder.

Repairing Thunderbird Folders

repair folder

Thunderbird comes with its own repair functionality built-into the email client. Do the following to use it:

  1. Right-click on the folder that you want to repair and select properties from the context menu. This opens the Folder Properties window. Note that this works only for folders, but not for entire email accounts.
  2. Locate and activate the Repair Folder button there. It should be visible right away, but if Thunderbird opens a tab you don't see it listed on, switch to the general information tab to locate it.
  3. I suggest you wait until the repair operation completes before you do anything else. Repeat the steps for any other folder in Thunderbird.

Fixing Thunderbird slow downs

thunderbird msf files fix slow downs

The problem is that these indexes can become corrupt over time which may cause the slow downs and hangs that some user experience in Thunderbird.

The easiest way to fix this problem is to delete the msf files in the Thunderbird profile folder after closing the Thunderbird email client. Thunderbird will automatically rebuild the indexes on its next startup fixing any problems that were caused by these files.

The easiest way to access the profile is by selecting Help > Troubleshooting information in Thunderbird, and there on the page that opens the "show folder" button. This opens the local profile folder

Note: It is of course recommended to backup the Thunderbird profile folder before deleting any files within (Check Backup Email Clients And Web Browsers).


Another possibility is to run a software program like ThunderFix. ThunderFix eliminates most of the hassle associated with the process.

It displays a list of Thunderbird profiles that it found on the computer system after execution. All it takes to delete all msf files associated with the profile is to select the profile and click on the Fix Profile link.

It is again recommended to backup the profile before running the software program.

While you may find that this is a viable solution for some slow down issues or freezes in Thunderbird, you may want to take a look at other possible solutions that help you speed up the email program on your system.

  1. Make sure you have configured Thunderbird to compact the mailboxes regularly to save space. You can do so under Tools > Options > Advanced > Network & Disk Space > Compact all folders when it will save over xx MB in total.
  2. If you do not rely on the global search, or notice that it slows down the email program, you may want to consider disabling it. You find that option under Tools > Options > Advanced > General > Enable Global Search and Indexer.
  3. If you are running add-ons in Thunderbird, try disabling those manually via Tools > Add-ons, or use Help > Restart with Add-ons Disabled to restart the email client with all extensions disabled for that session.
Fix Slow Or Hanging Thunderbird Email Client
Article Name
Fix Slow Or Hanging Thunderbird Email Client
The following guide provides you with instructions on fixing the Thunderbird email client when it becomes slow or hangs regularly.
Ghacks Technology News

Tutorials & Tips

Previous Post: «
Next Post: «


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

    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

      I think its thunderbird

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

      It is Mozilla Thunderbird.

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

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

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

    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

      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

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

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

      Fantastic. Thank you. Size did the trick.

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

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

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

    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

    You are a god – thank you!

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

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

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

    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

    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

    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

    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

      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

    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

    Great tip! Thanks!

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

    Worked for me, too – thank you!!!

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

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

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

    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

    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

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


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

    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

    Thank you, this worked !!!!

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

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

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

    Awesome, this post solved the issue. Many thanks!

Leave a Reply

Check the box to consent to your data being stored in line with the guidelines set out in our privacy policy

We love comments and welcome thoughtful and civilized discussion. Rudeness and personal attacks will not be tolerated. Please stay on-topic.
Please note that your comment may not appear immediately after you post it.