[Fix] Extension could not be Installed Because It is not Compatible with Thunderbird

If you use Mozilla Thunderbird desktop email client to send/receive emails and upgraded to a newer version, you might have noticed that some of your existing extensions/add-ons were automatically disabled by Thunderbird. Also if you try to install some of your favorite extensions in Thunderbird, it fails and you get following error message:

The extension could not be installed because it is not compatible with Thunderbird.

Following 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:

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Extension_Not_Installed_Incompatible_With_Thunderbird.png

So most of the extensions which used to work in older versions of Thunderbird, suddenly stopped working in newer Thunderbird versions.

It’s happening because of a new feature called “Strict Compatibility Enforcement Policy” introduced in Thunderbird 60.0 and later versions. This new policy will allow installation of only those extensions which have been explicitly marked as compatible with newer Thunderbird versions by their authors.

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.

Don’t worry! Thunderbird development team has provided a built-in preference to disable this strict compatibility enforcement checking mechanism. You can completely turn off the compatibility checker to opt-out from this new feature.

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 use following simple steps to install extensions/add-ons which are not marked as compatible explicitly in Thunderbird:

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1. Open Thunderbird and click on the Main Menu (3 horizontal lines) icon present at the extreme right corner of the toolbar. Now click on Options menu.

Alternatively, you can press ALT key to temporary show Menubar and then select “Tools -> Options” menu.

2. It’ll open Thunderbird Options window. Go to the last tab “Advanced“.

3. Click on the “Config Editor” button given at the bottom of the window.

Open_About_Config_Editor_Mozilla_Thunderbird.png

It’ll open hidden secret “about:config” page of Thunderbird which is similar to Mozilla Firefox‘s advance configuration editor page. It’ll show you a warning message, click on “I accept the risk!” button.

Related: [Tip] How to Access “About:Config” Page in Mozilla Thunderbird

4. Now type strictcom in Search filter box and it’ll show following preference in the window:

extensions.strictCompatibility

5. This preference is set to true by default i.e. enabled. To disable the feature, double-click on extensions.strictCompatibility preference and change its value to false. Alternatively, you can right-click on the preference and select Toggle option.

Disable_Extensions_Strict_Compatibility_Enforcement_Check_Thunderbird.png

That’s it. Now you have successfully disabled strict compatibility enforcement feature in Thunderbird. Now you can install your favorite extension/add-on again which was marked as incompatible by Thunderbird newer versions.

Published in: Mozilla Firefox, Troubleshooting Guides

About the author: Vishal Gupta (also known as VG) has been awarded with Microsoft MVP (Most Valuable Professional) award. He holds Masters degree in Computer Applications (MCA). He has written several tech articles for popular newspapers and magazines and has also appeared in tech shows on various TV channels.

Comments

NOTE: Older comments have been removed to reduce database overhead.

  1. I just installed thunderbird version 115.1.0
    I do not see how to get new messages
    Can you tell me how to do that?

  2. ^^ What exact problem are you facing? Please provide more details. Did you upgrade from old version or clean installed new version?

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