24, 31, 38 represent the version of Gecko that Thunderbird ships with. https://wiki.mozilla.org/Thunderbird/New_Release_and_Governance_Model https://wiki.mozil

24, 31, 38 represent the version of Gecko that Thunderbird ships with. https://wiki.mozilla.org/Thunderbird/New_Release_and_Governance_Model https://wiki.mozilla.org/Thunderbird/New_Release_and_Governa... Thunderbird now follows an Extended Support Release process, rolling out every eight release cycles equaling every 54 weeks. https://www.mozilla.org/en-US/thunderbird/organizations/faq/ https://www.mozilla.org/en-US/thunderbird/organizations/faq/ This is because Thunderbird is no longer in active development; it is primarily in maintenance mode. https://blog.lizardwrangler.com/2012/07/06/thunderbird-stability-and-community-innovation/ https://blog.lizardwrangler.com/2012/07/06/thunderbird-stabi...