You may know that I made the switch to a new version of Thunderbird some time ago which is currently available as an alpha release. Most of the extensions available for Thunderbird are not compatible with this version.
I never really bothered to find a solution for that since I did not make use of must-use extensions in the email client. It was however bothersome to run an earlier version of the email software side-by-side to test extensions.
I decided to investigate the issue to find a way to force compatibility in Thunderbird. The following guide should help all Thunderbird users who need to make an extension compatible.
I know of three methods to force compatibility in Firefox and since the programs share the same core it felt natural to begin there.
The best working method after some tests is in my opinion to override compatibility enforcement in the email client’s configuration. This is done the following way:
Start Thunderbird and open the configuration window by clicking on Tools > Options first. This opens the options window. Go to Advanced > General and click on the Config Editor button there.
The config editor opens in a new window. The directive does not exist by default which means that it needs to be added first. The general format of the parameter looks the following way:
extensions.checkCompatibility.Version
The version is always separated with a dot, e.g. 3.3. If Thunderbird is a release version that’s all that needs to be added. Alpha and beta versions on the other hand need to be specified individually by adding an a for alpha or b for beta behind the version.
The compatibility parameter for Thunderbird 3.3 alpha 2 is therefore
extensions.checkCompatibility.3.3a
To add it right-click in the configuration window and select New > Boolean from the list. A form pops up. enter the parameter name, e.g. extensions.checkCompatibility.3.3a and click ok. Now you need to select if the Boolean value should be true or false. True in this case is the default value which means that Thunderbird will check for extension compatibility. Since we do not want that we set the value to false. Restart the email client and install your extensions. Inactive extensions that have been inactivated because of incompatibilities should show up as activated.
And this is the result in the extension listing
Please note that forcing compatibility is no guarantee that the extension will actually work in Thunderbird. It is helpful if an extension developer has not updated the extension yet that is otherwise compatible with the version of Thunderbird.
You need to understand as well that the parameter that you have just configured needs to be adjusted whenever the version of the email client changes.
Update: The majority of tips outlined below work in newer versions of Thunderbird as well. In addition, you can also install the Disable Add-on Compatibility Checks extension for the email client for that as well now. It automates the process so that you don’t have to change the version of the parameter each time the program updates to a new version.