Sometimes somebody else has fixed the add-on and uploaded the newer version to the Add-ons mirror because it was too much hassle to submit it to the Mozilla add-ons web site.
If one isn't found, you can override the compatibility check.Most add-ons will work if you do that, but it can cause the application to behave improperly.Thunderbird will also disable the add-on and prevent you from enabling it by right clicking on the add-on in "Tools - Add-ons" and pressing the enable button.The first thing to try is to check for updates to see if a new version is available.Updates to installed plugins (such as Adobe Reader, Flash, and Quick Time) can be obtained from the website of the plugin provider or by visiting Plugin Doc.
To perform an update check: The Add-ons dialog will inform you if an existing add-on is incompatible with the current version of your application.see if there is an updated version at the Add-ons mirror.Some of the add-ons at Mozilla add-ons have been abandoned by the author.The original Thunderbird logo was just a modified Firebird logo, with a simple shifting of hue value from red to blue. On December 23, 2004, the Project Lightning was announced for tightly integrating calendar functionality (scheduling, tasks, etc.) into Thunderbird.In 2004, together with the change of Firefox's visual identity by Jon Hicks, a more professional logo that is currently in use was introduced. Lightning is just a project name, not a product name. The current version is 2.6, as at Thunderbird 24.01 release.Its initial focus was on the next major version, Thunderbird 3.0, which was released on December 8, 2009.