If you are using Mozilla's Thunderbird email client on a desktop computer, you probably have updated to version 12 of the client when the new version came out. Shortly thereafter, Thunderbird was updated to version 12.0.1, which resolved several issues that came to light after the final release of Thunderbird 12.
Some Thunderbird users ever since they have updated to Thunderbird 12 have noticed that the client's performance dropped considerably. This is for instance the case when affected users open emails in the program, as it may happen that it takes longer than usual to do so. Thunderbird in some instances may even freeze, for a while.
According to Mozilla, the most likely cause for this is antivirus software running on the system. Bugs have been filed by users running NOD32 and Avira Antivir, with the likelihood that other antivirus applications may cause the issues as well.
A workaround has been posted to fix the issue for affected users.
- Open the Thunderbird Profile Directory from Help | Troubleshooting Information
- Quit Thunderbird
- Delete any directories in the Thunderbird Profile Directory ending in "-wal" or "-shm"
- Then restart Thunderbird
- E.g. delete directories named like the following: "places.sqlite-wal", "places.sqlite-shm", "cookies.sqlite-shm", "cookies.sqlite-wal"
Users need to make sure that they only delete directories, and not files in the Thunderbird profile folder to test the fix. I'd suggest to make a backup of the profile folder - with Thunderbird closed- to avoid any issues that could result from this. MozBackup can do that for instance.
Once you have deleted the folders in the Thunderbird profile directory, restart Thunderbird to see if the issue has been resolved.
According to Mozilla, a patch for the issue is in the making to resolve it on their side of things. You find the full bug report listing here, in case you are interested or want to share your own experience. (thanks Sören)
Update: Please note that this fix only works for the issue described above. Thunderbird does not use these directories by default, which is why you probably won't find them listed in the client profile directory when you open it.
You can check out our guide on fixing a slow or hanging Thunderbird client for general tips to improve its speed or resolve the issue that you are experiencing when using it.
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