Sometimes some extensions don’t work exactly as they are supposed to. Maybe the version you are trying to install does not work with the Thunderbird version that you have, or other issues are in conflict that needs to be resolved first.
Note that most of the extensions should work as it is and if they are being updated regularly by the developer, there shouldn’t be any problem. But if you must need to install some kind of an add-on that isn’t getting installed as usual, you can follow the steps below. Also keep in mind that there is some risk involved in doing so, so be careful when you are following the steps below.
#1 Turn off the strict compatibility option:
Thunderbird has by default enabled the strict compatibility check for security purposes. This means that Thunderbird needs everything to updated and it checks for compatibility with strict measures. By turning it off, you can sometimes allow some extensions to be installed with your version, although with some risks:
- Go to Config Editor (Tools -> Options -> Config Editor, at the bottom). Accept the risk when prompted.
- Type “extensions.strictCompatibility” in the search box.
- Right click the “extensions.strictCompatibility” and select “Toggle” to turn it to ‘False’ from True. Or double-click it to do the same.
- Try installing the Thunderbird extension that you were trying.
#2 Disallow automatic updates:
This yet again can be slightly riskier as you might not receive the important updates that the developer wants to be rolled out. But sometimes new updates can make extension buggy or it won’t work at all. By turning off automatic updates, you gain back the control regarding updates and might update manually when you are sure it will work fine. To do it:
- Go to tools -> Add-ons
- Select ‘Extensions’ from the left side bar
- Click the three dotted icon next to the add-on that you feel is not working as it is supposed to be and then click “manage.”
- Inside the add-on options page, scroll below, and turn off “Allow Automatic Updates.”
#3 How to install an incompatible version anyway:
When you search for an add-on inside your installed Thunderbird edition, Thunderbird automatically disables the “Add to Thunderbird” button if the add-on is not compatible with the installed version of the client. But it also shows the options to “View Other versions.” This means you can view all the editions of the add-on and see which one is compatible with your installed edition of Thunderbird. And even if you do not find any that is officially compatible, you will find the option for “Download Anyway.”
This trick sometimes works even if Thunderbird is showing that the add-on is incompatible. However, its rare to be so. If you install the add-on anyway, you will likely find that Thunderbird gives you an error or that the add-on doesn’t work properly with all its features. In that case, your last resort is to revert back your Thunderbird to the older one where the add-on is fully compatible.
#4 Revert Thunderbird to older versions:
You can find our blog post about how to go back to the older version of Thunderbird: https://www.uslsoftware.com/go-back-to-the-older-version-of-thunderbird/