Before we start thinking about working on Thunderbird or its replacement there is a fundamental question that needs answering. Is there a future for email? Email is/was a function of the personal computer era. But as PC sales decline and smart phone sales grow do people still use email to the same extent? Is its place in field of personal communications being replaced by SMS, etc. In the business arena I am seeing some companies where internal email is not allowed. The reasoning is that email has become a way of procrastinating (send and forget). On the customer facing side of things email is being replaced by web based customer service apps that use AI (or similar) to answer the customers query ASAP, and if that is not possible get the info and pass on to a human if and only if needed (people cost money). So back to the question is email and by extension Thunderbird obsolescent. Would effort in redeveloping TB be futile as it would wind up give us wonderful app just as email disappears.