Standard diagnostic - Thunderbird
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This article is a step-by-step guide that users can follow if Thunderbird is not working properly and no other application is exhibiting strange behavior.
- Reboot the computer. If the problem persists, continue ...
- Close Thunderbird using "File -> Exit". And make sure it is not running in the background. Do not skip this step.
- Start Thunderbird in Safe Mode (not Windows Safe Mode) to disable all add-ons and use the default theme. If the problem exists in Safe Mode, or Thunderbird doesn't start in Safe Mode, continue to the next numbered step. If the problem goes away in Safe Mode ...
- Uninstall your most recently installed or updated extension or theme, and start Thunderbird normally. If the problem persists ...
- Select the default theme in "Tools -> Add-ons -> Themes" and uninstall your add-ons one at a time in "Tools -> Add-ons" (add-ons may appear grayed out, but can still be uninstalled). Perform step 3 again and start Thunderbird normally. If the problem persists, continue on.
- Important: Back up your profile before continuing to protect your settings and personal data (such as mail and passwords). Then,
- Perform step 2 again and delete the file "XUL.mfl" (Windows), "xul.mfasl" (Linux), or "XUL FastLoad File" (Mac OS X) from your profile folder. This file will be regenerated on next startup. If the problem persists ...
- Perform step 2 again, then delete the "localstore.rdf" file from your profile folder. You will lose any changes you have made to the toolbars. If the problem persists ...
- Perform step 2 again, then delete the "chrome" and "extensions" folders from your profile folder. You will lose all your add-ons and themes. If the problem persists ...
- Perform step 2 again, then create a NEW profile using Profile Manager. Your personal data and settings will be deleted if you delete the profile you are currently using. If the problem is resolved, selectively copy back your important profile data to the new profile. If the problem persists, continue on.
- Do a fresh install (this will NOT delete data in your profile):
- Uninstall Thunderbird.
- Open your program directory (Windows XP/2000: Start -> Run -> type %programfiles% -> OK, Windows 98/ME: Start -> Run -> type C:\Windows\Program Files -> OK) and if found, delete the folder named "Mozilla Thunderbird".
- Open your OS temporary directory (Windows XP/2000: Start -> Run -> type %temp% -> OK, Windows 98/ME: Start -> Run -> type C:\Windows\Temp -> OK) and delete all files and folders contained therein.
- Download the Thunderbird installer from mozilla.org and re-install.
If none of these steps help, the problem could be with other running programs such as a firewall, mail-screener, spamblocker, parental control or similar program that is conflicting with Thunderbird. Try disabling these other programs, one at a time. Also check your system for viruses, spyware and other malware. You might also run the procedure at  to test for performance issues.