Thunderbird has been around for 20 years, and that’s like saying centuries when talking about user interfaces and accessibility. The visual and usability paradigms that were the golden standards when the first version of Thunderbird was released are looked at like today we look at carts and horses as the fastest means of transportation. When Thunderbird was first released, tabs weren’t even a thing. Can you imagine using your OS without tabs at all? This talk will explore the years of UI evolution (and stagnation) of Thunderbird, and explain the reasons that drove us to the decision of reworking it entirely from scratch, which modern UI/UX we’re implementing, what challenges are we facing, and how our community is responding to this drastic “life shattering” event.