The Thunderbird email client had to take a back seat over at Mozilla when the organization decided to spend resources on other projects instead. While it is still maintained, for instance with regular security updates, there has not been any updates of note in recent time that added new features to the desktop email program.
If you have your Gmail email account linked in Thunderbird using IMAP, you may have noticed that emails do not arrive in a timely fashion anymore, that retrieving emails takes quite some time, and that it is slowing down the system in the process.
According to initial reports, users who make - heavy - use of labels are affected by this the most. The cause for the issue has been identified by Mozilla. According to a bug report, it is Google's recent introduction of CONDSTORE for all Gmail users that is causing the issues.
The Conditional Store facility provides a protected update mechanism for message state information that can detect and resolve conflicts between multiple writing mail clients.
The solution itself is rather simple at this point in time. Disable CONDSTORE in Mozilla Thunderbird to resolve the issue. That's not optimal but users who experience slow downs or other Gmail related issues in Thunderbird when using IMAP may want to give this a try to see if it fixes the issues they experience.
To disable CONDSTORE do the following:
- Click on Tools > Options in the menu bar.
- Select Advanced > General and click on Config Editor here.
- Type condstore in the search box and wait until the results are filtered automatically.
- The only result is the mail.server.default.use_condstore preference.
- It has a boolean value set to true (which means it is enabled).
- To disable it, double-click the name. This should set it to false.
Sören notes that there is also an undocumented preference that you can use to disable CONDSTORE for individual mail servers.
Use mail.server.server*.use_condstore where * is the number of a mail server to disable CONDSTORE for that mail server only. You can display server numbers by clicking on Help > Troubleshooting Information. Here you see account IDs, and the number next to those IDs indicate the server number.
Mozilla plans to disable CONDSTORE by default for all users in the next update. While no final decision seems to have been made in this regard, it is the most likely cause of action considering that it is currently unclear how many users of the email client are affected by this.