A problem I foresee is Firefox&#x27;s attempts to move away from XUL.[0] Firefox might just about manage that move, but who will do that work for Thunderbird? And once Firefox moves away from XUL, who will maintain XUL for Thunderbird&#x27;s sake?<p>[0] Firefox is still XUL-based for now, but I think the writing&#x27;s on the wall given the security issues with XUL and XPCOM, and Firefox&#x27;s move away from XUL&#x2F;XPCOM-based extensions.