There has been some rumbling today about the future of Thunderbird, starting with
Mitchell's call to action. Thunderbird has been a step-child of the Mozilla Corporation for quite some time while it spearheaded the rediscovery of the open web by spreading Firefox. This is an important job, but a company of perhaps 150 people or so working on Firefox and two working on Thunderbird just doesn't work out. I guess that time has come when MoCo has to split off the step-child mail client and become the Firefox Corporation that it has been acting as for a while now. In some way, mail client and browser get separated once again, some years after doing that on the technical application level.
This is a possibility for Thunderbird to step out of the shadow of its overwhelming browser brother if it's done right. Almost everyone,
including Scott as the head of Thunderbird development, is thinking the best option is to form Thunderbird into a community project like SeaMonkey, and Sunbird (or even Camino-like-Firefox).
I also think that a Thunderbird community project is a good solution for stepping out of Firefox' shadow, but I hope the organizational overhead can be kept as low as possible. We don't have any official organization for SeaMonkey, being backed "only" by the Mozilla Foundation, and that structure works well (the SeaMonkey development community might be bigger than Thunderbird's at the moment, despite probably the opposite is true for user numbers). Of course, Scott and David should still be paid for Thunderbird development, so there has to be some form of organization. Maybe we should even think about an organization that backs multiple Mozilla-based projects, or this can even be done via the Foundation itself? Let's see how this turns out.
In any case, the SeaMonkey project will happily team up with the Thunderbird project where useful, it's in the interest of both our projects to have a healthy and well-developed email and newsgroup backend, so we both can deliver top-quality software to our respective target audiences.
I wish the Thunderbird good luck on this interesting journey and hope that we can continue working well together for a good future of Mozilla-based Mail and News clients.