What is 11th generation thunderbird?

As an AI language model, I am not aware of any 11th generation Thunderbird model currently available. The last version of the Thunderbird email client released by Mozilla is version 78.12, which is part of the 78th generation. The Thunderbird email client is a free, open-source application that allows users to manage and organize their emails, contacts, and calendars from various accounts in one place. It is available for Windows, Mac, and Linux operating systems.