You can use following simple steps to install extensions/add-ons which are not marked as compatible explicitly in Thunderbird:ġ. If you want to install your favorite extension/add-on in Thunderbird 60.0 or later but it’s not compatible and Thunderbird is blocking the installation, you can disable the strict compatibility check feature to allow the installation of your desired extension. You can completely turn off the compatibility checker to opt-out from this new feature. If an extension is not marked as compatible with Thunderbird 60.0 or later, it’ll be disabled automatically and if you try to install an incompatible extension, it’ll be blocked immediately and you’ll get above mentioned error message.ĭon’t worry! Thunderbird development team has provided a built-in preference to disable this strict compatibility enforcement checking mechanism.

This new policy will allow installation of only those extensions which have been explicitly marked as compatible with newer Thunderbird versions by their authors. It’s happening because of a new feature called “ Strict Compatibility Enforcement Policy” introduced in Thunderbird 60.0 and later versions. So most of the extensions which used to work in older versions of Thunderbird, suddenly stopped working in newer Thunderbird versions. The extension could not be installed because it is not compatible with Thunderbird.įollowing screenshot shows the error message shown by Thunderbird when we tried to install an extension which was working fine in previous Thunderbird version without any issues:

Mozilla thunderbird download extensions